FLOUR    MILLING 


FLOUR  MILLING 

A  THEORETICAL  AND  PRACTICAL  HANDBOOK 

OF  FLOUR  MANUFACTURE 

FOR  MILLERS,  MILLWRIGHTS,  FLOUR-MILLING 

ENGINEERS,  AND   OTHERS    ENGAGED  IN  THE 

FLOUR-MILLING  INDUSTRY 


BY 

PETER    A.    KOZMIN 

OF  THE  POLYTECHNIC  INSTITUTE,  PETROGRAD 
EDITOR    OF    THE   RUSSIAN  MILLER 

TRANSLATED   FROM  THE   RUSSIAN 

M.    FALKNER   and   THEODOR   FJELSTRUP 


NEW    YORK 
D.    VAN    NOSTRAND    COMPANY 

25    PARK    PLAGE 
1917 


PREFACE 

IT  is  a  singular  fact  that  there  is  no  serious  modern  work  on  flour  milling 
in  English.  This  fact  was  recently  stated  by  Mr.  Arthur  E.  Hawker, 
secretary  of  the  National  Association  of  British  and  Irish  Millers,  in  a 
letter  to  the  Editor  of  Milling.  Even  the  rich  American  technical 
literature  has  no  modern  works  of  this  kind,  and  the  Americans  were 
compelled  four  or  five  years  ago  to  translate  the  old  book  of  Professor  Fr. 
Kick,  the  last  edition  of  which  was  published  over  twenty  years  ago  (1 894) . 

The  want  of  serious  scientific  literature  on  flour  milling  is  noticeable 
even  in  the  German  language,  in  which  dialect  during  all  the  time  which 
has  elapsed  since  the  appearance  of  Professor  Kick's  book  not  one  objective 
scientific  work  has  been  published.  As  a  characteristic  feature  of  the 
German  literature  of  the  last  few  years  (Baumgartner — 1902,  Baum- 
gartner  and  Graf — 190 4,  Baumgartner — 1907,  Pappenheim — 1903,Ketten- 
bach — 1907),  one  may  point  out  the  absence  of  descriptions  of  English 
and  American  machinery.  I  refrain  from  judging  whether  this  is  a 
result  of  the  Germans  not  being  acquainted  with  the  machinery  of  English 
and  American  manufacture,  or  whether  it  is  to  be  ascribed  to  the  peculiar 
German  patriotism  in  science.  Be  this  as  it  may,  the  German  authors 
do  not  give  a  broad  scientific  technical  statement  to  their  readers  when 
they  omit  to  mention  English  and  American  machinery. 

Having  been  for  twenty  years  engaged  in  this  industry  as  a  theoretical 
and  practical  worker,  and  having  studied  the  technology  of  milling  in 
Russia,  Germany,  Austria,  Hungary,  France,  Belgium,  England,  and 
the  United  States,  I  made  up  my  mind  to  write  a  book  on  this  subject, 
keeping  to  the  most  scientific  basis.  The  object  I  had  in  view  was  to 
produce  a  practical  and  theoretical  text-book  for  operative  millers  and 
for  milling  engineers,  who  have  to  construct  flour  mills  and  to  design 
flour  milling  machinery. 

I  thought  it  necessary  to  begin  my  book  with  an  historical  outline  of 
the  manufacture  of  flour.  I  drew  up  this  outline  on  the  basis  of  the 
materials  which  I  found  in  the  richest  library  of  the  world,  that  of  the 
British  Museum,  as  well  as  in  the  Congressional  Library  of  the  United 


382938 


vi  PREFACE 

States,  in  which  I  worked  on  the  occasion  of  my  visits  to  these  two 
countries.  I  have  given  an  outline  of  the  most  important  development 
the  milling  industry  has  undergone  from  the  ancient  period  of  the  civilised 
nations  of  Asia  Minor  and  Egypt  till  the  period  when  practice  determined 
the  correct  way  of  improving  the  technology  of  flour  milling.  The 
historical  outline  is  important  in  that  it  presents  the  general  development 
of  the  craft  to  the  mind  of  the  student  and  forces  him  to  think  more 
logically. 

After  having  spoken  of  the  product  which  is  to  be  treated,  I  pass  to 
the  study  of  the  construction  of  the  cleaning  and  grinding  machines. 
The  designs  of  the  machines  performing  a  very  particular  operation  in 
the  cleaning  and  grinding  processes  are  almost  infinitely  variable.  In 
order  to  train  the  student  promptly  and  logically  to  analyse  and  estimate 
the  numerous  machines,  I  have  classified  them  according  to  the  principles 
of  their  action,  having  pointed  out  the  most  economical  principles  of 
operation.  Then  I  have  illustrated  the  fundamental  principles  from  the 
most  characteristic  and  most  popular  European  and  American  machines. 
To  explain  my  idea,  I  will  take  for  instance  the  study  of  the  roller  mill. 
I  consider  this  machine  from  the  point  of  view  of  feeding  the  rolls  (German, 
English,  and  American  systems  of  feeding),  disposition  of  the  rolls  (hori- 
zontal, vertical,  or  diagonal),  driving  of  the  rolls  (gear  drive  in  the  European 
makes,  belt  drive  in  America),  methods  of  ventilation,  etc.  Describing 
the  principles  of  the  action  and  design  of  certain  machines,  I  make  also 
a  critical  estimate  of  them,  basing  my  contentions  on  practical  and  scientific 
considerations. 

Such  is  my  method  of  describing  machines,  the  idea  always  being  to 
give  the  student  a  conception  of  the  most  important  designs  and  to  force 
him  to  think  critically. 

In  the  chapter  on  milling  diagrams  I  give  typical  diagrams  of  systems 
at  work  in  European  and  American  countries,  in  order  that  the  student 
may  compare  all  the  different  schemes  of  grinding. 

In  each  chapter  I  give  the  practically  established  capacities  of  the 
machines  and  a  basis  for  the  calculation  of  the  necessary  number  and 
dimensions  of  them  corresponding  to  a  given  capacity  of  a  Russian, 
German,  English,  or  American  mill. 

No  author  has  as  yet  paid  attention  to  the  problem  of  the  motion  of 
the  plansifter  and  of  the  movement  of  the  product  in  the  purifier.  I 
thought  it  therefore  necessary  to  solve  this  problem,  and  this  makes 
it  possible  scientifically  to  estimate  the  advantages  and  disadvantages 
of  the  different  types  of  these  machines. 


PREFACE  vii 

In  writing  my  book  I  have  attempted  to  instruct  and  prepare  the 
way  for  learned  and  scientifically  thinking  specialists.  It  is  for  others 
to  judge  as  to  whether  I  have  succeeded  in  my  achievement. 

In  writing  this  book  I  have  largely  availed  myself  of  the  materials 
and  advice  of  my  professional  colleagues  working  theoretically  and 
practically  in  England  and  America  for  the  benefit  of  the  Milling  Industry. 
I  consider  it  therefore  my  duty  most  earnestly  to  thank  Mr.  W.  Jago, 
the  author  of  the  excellent  work  on  The  Technology  of  Bread  Making, 
for  his  kind  permission  to  reproduce  some  of  its  tables  and  photographs 
of  the  wheat  grain.  Further,  to  Mr.  R.  A.  Sidley,  editor  of  The  Miller  ; 
to  Mr.  Geo.  J.  S.  Broomhall,  editor  of  Milling  ;  Mr.  A.  R.  Tattersall,  Mr. 
Chas.  E.  Oliver  of  the  Dixie  Miller,  and  many  others  who  have  rendered 
me  their  kind  assistance. 

In  addition,  many  English  and  American  firms  have  supplied 
me  with  detailed  drawings  of  their  machines,  which  I  have  reproduced 
in  my  book.  I  am  therefore  most  grateful  to  Messrs.  Thos.  Robinson  & 
Son,  Rochdale,  England  ;  Messrs.  E.  R.  &  F.  Turner,  Ipswich,  England  ; 
Messrs.  Nordyke  &  Marmon  Co.,  Indianapolis,  Ind.,  U.S.A.  ;  Messrs. 
The  S.  Howes  Co.,  Silver  Creek,  N.Y. ;  Allis-Chalmers  Co.,  Milwaukee, 
Wis.  ;  and  many  others. 

Finally,  I  desire  to  express  my  heartiest  thanks  to  Messrs.  Geo. 
Routledge  &  Sons  Ltd.,  for  their  kind  consent  to  publish  my  book  in 
English,  and  thus  to  give  me  a  chance  to  offer  it  to  the  judgment  of 
the  specialists  of  England  and  America,  to  whom  I  shall  be  most  obliged 
for  their  impartial  criticism. 

P.  KOZMIN. 


PUBLISHERS'   NOTE 

The  Publishers  desire  to  add  their  thanks  to  Mr.  Edward  Bradfield, 
Associate  and  Technical  Editor  of  Milling,  for  his  assistance  in  revising 
the  proof  sheets  of  this  book. 


CONTENTS 


PAGE 

PREFACE                          .            .            .            .            ...  .  v 

CHAPTER    I 
HISTORICAL  OUTLINE  OF  FLOUR  MILLING 

I.  FLOUR  MILLING  ACCORDING  TO  RELIGIOUS  LEGENDS  AND  CLASSICAL  LITERA- 
TURE.    MODERN  RELICS  OF  ANCIENT  FORMS  OF  MILLING  .  .  .1 

II.  TYPES  OF  MILLS  DRIVEN  BY  ANIMAL  POWER              .            .  .  .11 

III.  THE  UTILISATION  OF  WATER  POWER  FOR  MILLS          .            .  .  .16 

IV.  THE  AMERICAN  AUTOMATIC  MILL  .         .            .            .            .  .  .23 

V.  THE  INFLUENCE  OF  AMERICAN  TECHNICS  IN  EUROPE              .  .  .26 

VI.  MILLS  IN  FRANCE  ........      27 

VII.  PROGRESS  OF  TECHNICS  IN  GERMANY    .            .            .            .  .  .29 

VIII.  FURTHER  DEVELOPMENT  OF  MILL  BUILDING  IN  EUROPE         .  .  .34 

IX.  THE  STRUGGLE  BETWEEN  THE  ROLLER  AND  STONE-MILLS       .  .  .37 

CHAPTER    II 
GENERAL  IDEAS  OF  THE  RAW  MATERIALS  FOR  FLOUR  PRODUCTION 

I.  THE  BERRIES  OF  THE  CEREALS  .            .            .            .            .  .  .39 

II.  PHYSICAL  STRUCTURE  OF  THE  WHEAT  GRAIN               .            .  .  .41 

III.  CHEMICAL  COMPOSITION  OF  WHEAT        .            .            .            .  .  .47 

CHAPTER    III 

PREPARATION  OF  GRAIN  FOR  GRINDING 

I.  IMPURITIES  AND  THE  PRINCIPLES  OF  CLEANING           .            .  .  .58 

II.  EXTRACTION  OF  PIECES  OF  METAL  FROM  THE  STOCK  .            .  .  .59 

III.  SEPARATION  OF  LARGE  AND  SMALL  IMPURITIES           ..            ..-  .  .61 

1.  Separation  according  to  Size        .             .             .             .  .  .61 

2.  Separation  according  to  Shape     .             .            .            .  .82 

IV.  MACHINES  FOR  SEPARATING  STONES       .            .            .            .  .  .92 

b  ix 


£  CONTENTS 

PAGE 

V.  SCOURING  AND  POLISHING  THE  GRAIN  .  .  .  .  .93 

1.  Principles  of  the  Processes  and  the  Character  of  the  Working  Parts     .       93 

2.  Construction  of  Scouring  Machines          .  .  .  .  .100 

3.  Special  Machinery  .  .  .  .  .  .  .118 

4.  The  Wet  Scouring  and  Washing  Process  ....     120 

VI.  DAMPING  THE  GRAIN       .  .  .  .  .  .  .  .     143 

VII.  GRAIN- CLEANING  DIAGRAMS  147 


CHAPTER   IV 
GRINDING  THE  GRAIN 

I.  THE  FUNDAMENTAL  PRINCIPLES  OF  MILLING   .            .            .  .  .153 

II.  THE  CONSTRUCTION  OF  THE  GRINDING  MACHINES        .            .  .  .155 

III.  MACHINES  OF  REITERATED  ACTION  OF  THE  WORKING  SURFACES  .  .156 

1.  Stone  Mills — Horizontal  (Vertical  Axis  of  Rotation)       .  .  .     157 

2.  Composition  and  Design  of  Millstones     .             .             .  .  .160 

3.  Under-Runner  Millstones              .             .             .             .  .  .180 

4.  Stone  Mills — Vertical  (Horizontal  Axis  of  Rotation)       .  .  .     187 

5.  The  Capacity  and  Calculation  of  Stone  Mills       .             .  .  .191 

6.  Mills  with  Metal  Grinders             .             .             .             ..      -  .  .195 

IV.  MACHINES  ACTING  BY  IMPACT   .            .            .            .            .  .  .     198 

V.  MILLING    MACHINES    HAVING    THE    Axis   OF    ROTATION   OF    THE  WORKING 

ORGANS  IN  DIFFERENT  PLANES          .            .            .            .  .  .     204 

VI.  ROLLER  MILLS     .            t           .            .           ,            .            .  ,  .    209 

1.  Conditions  of  Reduction  of  the  Product .           '.             .  .  .209 

2.  Corrugating  the  Rolls       .             .-         .  .             .             .  .  .     218 

3.  Adjustment  of  the  Distance  between  the  Working  Surfaces  .  .     233 

4.  A  General  Survey  of  the  Roller  Mill        .            .             .  .  .236 

5.  The  Feeding  of  the  Rolls              .             .             .             .  .  .243 

6.  Types  of  Roller  Mills 258 

7.  Transmission  of  Motion  to  the  Rolls        .....     296 

8.  Capacity  of  Roller  Mills    .             .             .             .          -  .  .  .299 

9.  Brush  Machines    .             .             .             .             .           '  •  •  .312 
10.  Detachers              ........     313 

CHAPTER    V 
GRADING  THE  PRODUCT  ACCORDING  TO  SIZE 

I.  SIFTING  THE  PRODUCT    .            .            .            .            .            .  .  .316 

II.  RELATIVE  POSITION  OF  THE  SIEVES      .            .            .            .  .  .     326 

III.  THE  SIFTING  PROCESS                             .                         .            .  .331 


CONTENTS  xi 

PAGE 

IV.  CONSTRUCTION  or  SIFTING  MACHINES    .            .            .  f            t                 335 

1.  Reels  and  Centrifugals      .             .            .  335 

2.  Plans  if  ters  *>AA 

•  •                       •                       *        Orrrr 

3.  Dynamics  of  Plansifters  .             .    •    '    ,    "         .  3^5 

4.  American  Sifters               .'          .            .            .  374 

5.  Free  Swinging  Plansifters             .          . .            .  382 

6.  Capacity  of  Plansifters     ....  386 


CHAPTEE   VI 

GRADING  THE  PRODUCT  ACCORDING  TO  SPECIFIC  GRAVITY 

I.  GRADING  MIDDLINGS  AND  DUNST  ACCORDING  TO  SPECIFIC  GRAVITY.           .  392 

II.  MIDDLINGS-  AND  DUNST-GRADING  MACHINES  OF  TO-DAY        .            .            .  406 

III.  CAPACITY  OF  PURIFIERS              .            .            .            .            .            .  420 

CHAPTER,   VII 

ACCESSORY  APPLIANCES  AND  MECHANISMS 

I.  PURIFICATION  OF  THE  INTERMEDIATE  PRODUCTS          .            .            .            .  423 

II.  DUST -COLLECTORS             ........  426 

III.  EXHAUST  SYSTEMS            ........  434 

1.  Group  Exhaust  Systems  .             ......  434 

2.  General  Exhaust  Systems             ......  438 

3.  Calculation  for  an  Exhaust  Plant             .....  442 

IV.  TRANSPORTATION  OF  STOCK        .            .            .            .                        .            .  445 

1.  Spouts  and  Elevators       .......  445 

2.  Horizontal  Transport       .......  458 

V.  APPARATUS  FOR  MIXING  AND  PACKING  FLOUR            ....  469 

VI.  APPARATUS  FOR  RECKONING  AND  REGULATING  THE  QUANTITY  OF  PRODUCT  476 

VII.  FLOUR  BLEACHING           .            .            .            .            .            .            .            .  480 

CHAPTER   VIII 
MILLING  DIAGRAMS 

I.  CLASSIFICATION  OF  MILLING  SYSTEMS    .            .            .            .            .            .  489 

II.  PLAIN  GRINDING  .  .  ..  ...  .491 

III.  DIAGRAMS  OF  IMPROVED  PLAIN  MILLING  SYSTEMS      .                                   .  494 

IV.  HIGH  GRINDING  .             .           '.            ...            .            .  500 

V.  SHORTER  GRADUAL  REDUCTION  SYSTEMS         ,.            .            .  511 

VI.  RYE  GRINDING  .    ,        .  .  .527 


xii  CONTENTS 

PAGE 

VII.  MAIZE  GRINDING             .            .            .            .            .        ^    .  .            .536 
VIII.  SCHEME  OF  OATMEAL  GRINDING            .           •.            .            .  .  v           .  538 
IX.  QUANTITY  OF  INTERMEDIATE  PRODUCTS  AND  THE  CALCULATION  OF  CORRE- 
SPONDING MACHINES    .            .            .            .            .            .  ."          .  541 

X.  RUSSIAN  GRINDING         .            .            .            .            .            .  "  .            .  547 

CHAPTER    IX 
CONSTRUCTION  OF  MILL  BUILDINGS 

I.  CONDITIONS  DETERMINING  THE  CHARACTER  OF  BUILDINGS     .  .            .  554 

II.  CONSTRUCTION  OF  MILL  BUILDINGS       .            .            .            ,  .  559 

III.  BUILDINGS  OF  COMPLICATED  GRINDING  MILLS             .            .  .            .  561 

IV.  CONSTRUCTION  OF  AMERICAN  MILLS      «            .            .            .  .            .  565 
V.  PLANS  OF  MILLS              .            .            .                        .            .  .            .  570 

CHAPTER    X 

THE  COST  OF  ERECTING  AND  OF  WORKING  MILLS 

I.  THE  MILL  BUILDING  AND  EQUIPMENT              .            .            .  .            .  575 

II.  CALCULATION  OF  WORKING  EXPENSES    .            .            .            .  .            .  577 

III.  SELECTION  OF  A  PRIME  MOTOR              .            .            .            .  .            .  579 

INDEX  .  583 


FLOUR   MILLING 

CHAPTER   I 

HISTORICAL    OUTLINE    OF   FLOUR   MILLING 


FLOUR  MILLING   ACCORDING   TO   RELIGIOUS   LEGENDS   AND   CLASSICAL 
LITERATURE.     MODERN  RELICS  OF  ANCIENT  FORMS  OF  MILLING 

MODERN  culture  of  mankind,  indissolubly  connected  with  the  technics 
of  production,  is  the  last  link  of  a  long  chain  of  human  endeavour  stretch- 
ing away  into  the  dark  space  of  past  millenniums. 

The  culture  of  mankind  has  not  developed  spasmodically ;  although 
history  relates  of  whole  peoples  vanishing  and  their  culture  with  them, 
this  is  but  a  seeming  disappearance  of  culture.  It  is  an  undoubted  fact 
with  us,  that  a  more  perfect  technical  knowledge  corresponds  with  a 
more  perfect  culture.  Culture  never  vanished,  it  simply  underwent  an 
evolution.  Its  old  forms  were  gradually  modified  and  perfected. 

When  studying  the  history  of  the  technics  of  any  particular  kind  of 
production,  we  come  to  the  conclusion  that  the  perfecting  of  the  process 
of  production  was  never  brought  about  by  leaps  and  bounds.  On  the 
contrary,  it  has  been  a  slow  process  of  gradually  collecting  grains  of 
human  knowledge.  Out  of  an  inexhaustible  source  of  knowledge,  the  gains 
of  culture,  i.e.  the  weapons  of  the  victorious  battle  of  man  for  existence 
and  happiness,  passed  from  one  people  to  another ;  neither  racial,  social, 
nor  national  and  territorial  partitions  of  humanity  could  bar  their 
passage.  An  empire  might  vanish,  even  a  people,  but  the  weapons  of 
the  struggle  for  life — in  the  first  place,  the  implements  of  production — 
remained  in  the  hands  of  others,  and  the  culture  did  not  disappear. 

The  law  of  evolution  of  the  technics  of  production  is  a  curve  having 
no  solution  of  continuity.  The  study  of  the  development  of  a  produc- 
tion gives  us  the  law  of  inflection  'in  that  curve.  Parallel  to  this 
curve,  i.e.  in  accordance  with  that  law,  runs  uninterruptedly  the  line 


2  :^f>UR   MILLING  [CHAP,  i 

of  human  culture.  That  is  the  reason  why  historical  catastrophes  of 
human  culture  are  impossible,  however  powerful  the  wave  of  barbarians 
on  the  cultured  people  may  be. 

An  intimate  acquaintance  with  technical  history  is  indispensable 
to  every  engineer,  because  history  gives  us  the  law  of  evolution  of  the 
implements  and  processes  of  production.  Only  by  carefully  studying  the 
historical  development  of  the  technics  of  production  does  the  creative 
power  of  an  engineer  receive  its  true  education  and  evade  retrogression. 

The  most  brilliant  example  of  culture  and  its  evolution  to  date 
is  the  technics  of  procuring  and  preparing  the  nutritive  substances  for 
food.  Since  man  left  the  cave  epoch  behind  him,  vegetable  food  has 
constituted  undoubtedly  the  most  substantial  part  of  his  nourishment. 
Even  the  biblical  legend  of  paradise  tells  us  that  man  lived  on  the 
abundance  of  the  fruits  of  the  earth,  and  was  allowed  to  use  them  for 
food.  Traditions  about  a  human  paradise  on  earth  reached  even  the 
time  of  Ovid,  who  depicts  the  life  of  primeval  man  as  the  golden  epoch, 
when  men  were  content  with  the  food  the  earth  yielded  them  without 
constraint.  But  people  multiplied,  formed  numerous  groups,  the 
abundance  of  the  fruits  of  the  earth  did  not  suffice,  and  the  curse  of  pro- 
curing food  by  the  sweat  of  man's  brow  began  to  gain  ground.  The 
struggle  against  that  curse  is  the  history  of  human  culture,  the  history 
of  the  technics  of  production.  In  the  end,  a  perfect  technical  knowledge 
will,  of  necessity,  liberate  mankind  from  this  curse. 

Since  time  immemorial,  bread  has  been  the  most  essential  element  of 
man's  vegetable  food.  How  it  happened  that  man  stumbled  upon  the 
cereals,  why  he  began  to  cultivate  this  unsightly  plant,  we  know  not,  but. 
in  selecting  the  cereal  plant  out  of  the  mass  of  other  fruit,  man  made  no 
blunder,  for  the  grain  of  corn  contains  more  nutritive  substance  than 
any  other  fruit ;  but  out  of  the  gloom  of  ages,  traditions  slightly  varying 
in  import  have  reached  us.  Moses  says  that  Cain  tilled  the  soil,  that 
Noah,  after  the  flood,  likewise  began  to  cultivate  land.  Pliny  speaks  of 
a  tradition  which  ascribes  the  origin  of  agriculture  to  a  deity.1 

Tradition  tells  us  men  were  taught  to  cultivate  corn  by  the  goddess 
of  agriculture,  Ceres  (by  Demeter,  sister  of  Zeus,  according  to  the 
Greeks).  "  Before  this,  people  fed  on  acorns."  Pliny  adds  that  men 
learned  the  grinding  of  corn  to  flour  also  from  Ceres. 

From  this  myth  we  understand  that  the  art  of  grain  grinding,  a 
contemporary  of  agriculture  and  proceeding  from  one  and  the  same 
deity,  has  its  origin  in  the  same  depth  of  ages  as  the  cultivation  of  corn. 

1  Pliny  the  Elder  (A.D.  23-79),  Historic,  Naturalis. 


CHAP,  i] 


FLOUR   MILLING 


A  Spartan  tradition  ascribes  the  art  of  making  flour  to  Miles,  and  says 
that  the  chief  milling  town  in  Greece  of  that  epoch  was  Alesia. 

According  to  Hommel,1  Asia  is  the  native  country  of  the  cultivated 
cereals.  He  maintains  that  the  Sumerians  coming  to  Egypt  from 
Mesopotamia,  eight  thousand  years  ago,  had  a  great  influence  on  the 
culture  of  Egypt,  having  taught  the  aborigines  to  procure  and  work 
metals  and  cultivate  corn. 

About  the  grinding  instruments  of  the  pre-mythological  ages  the 
traditions  give  us  no  information,  but  relics  of  the  classical  and  the 
Egyptian  culture  exist,  which  can  give  -us  an  idea  what  the  antique 
Egyptian  machine  was  like. 

Excavations  and  the  hieroglyphics  of  the  ancient  Egyptians  indicate 
that  the  primitive  milling  implements  were  first  wooden,  then  stone, 


FIG.  1. — Grinding  in  Ancient  Egypt. 

and  later  on  metal  mortars,  in  which  the  grain  was  crushed  by  blows 
from  pestles.  Fig.  1  shows  the  whole  process  of  flour-making  by  the 
Egyptians.  This  drawing  is  a  reproduction  from  one  of  the  pictures 
that  decorated  the  house  walls  in  the  town  of  Thebes,  according  to 
Wilkinson's  Account  of  the  Ancient  Egyptians. 

The  mortars  here  are  marked  a,  the  pestles  with  two  working  ends  b, 
the  basket  of  grain  or  semi-product  d,  the  basket  of  ready  flour  c.  The 
loading  (/)  is  done  by  a  man,  who  pours  the  grain  out  of  the  vessel  g 
into  the  mortar.  Two  men  (//)  are  grinding ;  one  (///)  is  emptying  the 
crushed  grain  out  of  the  mortar  into  a  sieve  ;  the  last  man  (IV)  is  sifting. 
The  sifting  of  crudely-crushed  grain  was  known  apparently  even  in  these 
very  remote  times.  The  sieve  e,  a  kind  of  rudely-shaped  plate,  was  prob- 
ably made  of  papyrus. 

On  either  side  of  the  bas-relief  at  the  top  are  hieroglyphic  inscriptions 
h  and  /,  explaining  the  meaning  of  the  picture.  It  is  supposed  that  the 

1  Fr.  Hommel,  Prehistorische  Indo-Europeer. 


4  FLOUR   MILLING  [CHAP,  i 

ancient  Egyptians  roasted  or  heated  the  grain  until  dry,  previous  to 
grinding  it.  That  is  very  possible,  as  the  dryer  the  grain  is,  the  more 
easily  it  is  broken  by  blows  from  the  pestle. 

The  same  type  of  the  primitive  mill  existed  in  ancient  Greece,  and 
some  of  the  excavated  vases  bear  the  drawing  of  a  similar  mortar  and 

pestle.  Besides  that, 
Pliny  gives  us  a  de- 
scription of  apparently 
similar  mills  in  Greece, 
saying  that  "  in  Etruria, 
the  ears  of  corn  are 
roasted,  and  then 
crushed  by  means  of 
pestles  with  sharp  saw- 
like  edges  below  and 
a  cogged  wheel  in  the 
middle."  And  yet  the 
primitive  milling  in 
Etruria  required  tech- 
nical knowledge,  for 
Pliny  says  (ibid.)  if  the 
work  was  done  care- 
lessly,  the  grain  was 
crushed  more  finely 
than  was  necessary  and 
the  iron  parts  of  the 
pestle  were  soon  worn 
out  or  broken. 

But  what  strikes  us 
most  is  the  fact  that 
after  thousands  of  years 
living  relics  of  antique 
Egyptian  technics  are 
found.  Some  of  the 

negro  tribes  in  the  valley  of  the  Nile  use  the  mortar  and  pestle 
for  grain  grinding  at  the  present  day.  The  photograph  (Fig.  2) 
shows  a  striking  likeness  between  the  milling  of  a  negro  tribe 
near  Khartum l  and  that  of  ancient  Egypt.  Here  are  the  same  two 
baskets — one  with  grain,  the  other  for  flour — a  stone  mortar,  and 

1  Elis6e  Reclus,  L'Homme  et  la  Terre,  vol.  ii. 


FIG.  2. — Negro  Milling  at  the  Present  Time  in  Africa. 


CHAP.    I] 


FLOUR    MILLING 


wooden  pounder.       There  is  but  a  sieve  wanting  to  make  the  picture 
identical. 

In  China,  where  traditions  of  great  antiquity,  concerning  gramen, 
the  gift  of  gods,  also  exist,  wheat  was  cultivated  2700  years  B.C.  and  the 
ancient  Egyptian  type  of  grinding  machine  was  in  use.  Until  recently, 
in  many  parts  of  China  the  mortar  and  pestle  were  used  for  clipping  and 
polishing  rice,  i.e.  freeing  it  of  the  coatings.  In  several  out-of-the-way 
places  in  that  country,  wheat  is  still  crushed  to  a  coarse  flour  in  that 
mortar.  Fig.  3  represents  such  a  mill  supplied  with  a  foot  drive.1 


FIG.  3. — A  Chinese  Mill  of  the  most  Ancient  Type. 

An  interesting  mill  of  a  similar  type,  but  driven  by  water,  is  described 
by  Bridd  2  in  the  American  Miller. 

This  mill  (Fig.  4)  is  used  by  the  Indians,  who  settled  in  the  state  of 
Kentucky,  for  maize-grinding.  The  mortar  is  hollowed  out  in  a  tree 
stump.  A  lever,  with  a  stone  pestle  attached  to  one  end,  and  a  box  to 
the  other,  is  placed  on  a  fork.  A  jet  of  water  from  a  stream  is  con- 
ducted along  a  groove  into  the  box.  When  the  box  is  filled  with  water, 
outweighing  the  stone,  it  drops  to  the  lower  position,  the  water  runs  out 

1  Staunton,  British  Ambassador  in  China.     His  Report  to  the  Embassy  1797, 

2  American  Miller,  1907. 


FLOUR    MILLING 


[CHAP,  i 


FIG.  4. — Indian  Water-mill  in  Kentucky, 


of  the  box,  and  the  pestle  falls  quickly  into  the  mortar,  crushing  the  grain. 
The  capacity  of  the  mortar  is  about  28  Ibs.  of  grain;  that  quantity  is 
ground  in  eight  to  ten  hours. 

The  mill,  consisting  of  a  mortar  and  pestle,  belongs  to  the  first  period 

of  prehistoric  technics. 

The  next  stage  of  its  develop- 
ment is  a  transitory  type  from 
the  mortar  and  pestle  to  two  mill- 
stones, between  which  the  grain  is 
ground. 

The  primitive  type  of  such  a 
mill 1  was  produced  apparently  also 
in  Egypt  (Fig.  5).  The  grain  was 
ground  on  the  larger  stone  by  means 
of  the  small  one. 

We  find  this  mill  nowadays  in 
the  hands  of  the  natives  of  Africa 
in  the  Nile  Valley.  Fig.  6  represents  a  negress  preparing  flour  in  the 
same  manner  Egyptians  did  some  4000  years  ago.  Fig.  7  shows  the 
up-to-date  milling  of  the  Nu- 
bians. The  work  is  performed 
by  children  here. 

It  is  curious  to  note  that 
the  same  principle^  of  milling 
has  been  retained,  up  to  this 
day,  by  the  Mexican  Indians, 
who  are  considered  to  be  the 
descendants  of  the  Aztecs. 
Fig.  8  reproduces  that  "  mill  " 
used  by  Mexican  Indians  of  to- 
day ;  they  grind  their  corn  on  it. 
These  illustrations  of  primi- 
tive grain- crushing  show  us 
how  slowly  ancient  man  ac- 
quired the  principles  of  a  more 
economical  system. 

The  mill  of  the  first  type  is  very  simple — it  is  based  on  the  impact 
principle.  The  primeval  man  had  no  difficulty  in  coming  upon  this 
principle,  knowing,  as  he  did,  the  destructive  power  of  a  blow  and  the 

1  Photo  of  a  stone  implement  found  at  the  excavations  in  Upper  Egypt, 


FIG.  5. — Ancient  Egyptian  Milling. 


CHAP.    I] 


FLOUR   MILLING 


solidity  of  stone,  for  he  fashioned  his   axes  and  arrowheads  from  that 
material. 

But  gradually  the  human  mind  became  conscious  that  such  work  is 
not  efficient.  It  is  evident, 
besides,  that  the  blows  of  the 
pestle,  by  degrees,  wear  out 
the  mortar  and  the  pestle 
itself. 

Thus  the  question  of  the 
greatest  efficiency  of  work 
and  of  a  better  constructed 
machine  arises.  The  impact 
principle  is  rejected,  and 
that  of  grinding  is  adopted. 

That  principle  was  ad- 
hered to  in  the  mills  of  the 
improved  type,  that  might 
be  called  "  grinding  mills," 
for  thousands  of  years. 

When  the  mills  consisting 
of  two  grindstones  appeared 
is  not  known.  At  any  rate, 
it  may  be  supposed  that  they 
made  their  appearance  in 
Egypt,  and  3500  years  be- 
fore our  time  at  the  very  latest.  The  Jews,  leaving  Egypt,  doubtless 
brought  much  technical  knowledge  of  various  productions  out  with  them. 


FIG.  6. — Negro  Milling  to-day  in  the  Nile  Valley. 


FIG.  7. — Modern  Milling  :  Natives  of  Nubia. 

It  was  from  the  Egyptians  that  they  learned  to  grind  their  grain  to 
flour  on  millstones.  We  find  traces  of  that  fact  in  the  fifth  book  of 
Moses  (xxiv.  6),  where  it  is  written,  "  No  man  shall  take  the 


8  FLOUR    MILLING  [CHAP,  i 

nether  or  the  upper  millstone  to   pledge."     Evidently  the  grindstone 

mill  was  an  indispensable  utensil  of   a  Hebrew  household   during  their 

searches  for  the  blessed  land,  since  Moses  forbade  by  law  loans  on  the 

pledge  of  a  millstone. 

In    the    fourth    book    of    Moses    (xi.    8)    the    heavenly    manna    is 

spoken  of  in  the  following 
terms  ;  "  And  the  people  went 
about  and  gathered  it  in  mills, 
or  beat  it  in  a  mortar." 

The  contemporary  use  of  the 
mortar  and  grinding  mill  points 
to  the  period  of  the  migration 
of  the  Jews,  as  the  beginning 
of  the  use  of  grinding  mills, 
which  at  the  time  had  not 

yet  succeeded  in  supplanting  the  pestle  and  mortar. 

Grinding  mills  are  spoken  of  more  definitely  (about  1000  years  B.C.) 

in  Homer's  Odyssey  (song  7,  vv.  103,  104),  where  domestic  life  at  the 

court  of  King  Alcinous  is  described  : l 

"  Full  fifty  handmaids  form  the  household  train ; 
Some  turn  the  mill,  or  sift  the  golden  grain." 

and  then  canto  20,  vv.  105-111  :  2 

"  Beneath  a  pile  that  close  the  dome  adjoin'd, 
Twelve  female  slaves  the  gift  of  Ceres  grind  ; 
Task'd  for  the  royal  board  to  bolt  the  bran 
From  the  pure  flour  (the  growth  and  strength  of  man). 
Discharging  to  the  day  the  labour  due, 
Now  early  to  repose  the  rest  withdrew  ; 
One  maid,  unequal  to  the  task  assign'd, 
Still  turned  the  toilsome  mill  with  anxious  mind." 

The  grindstones  of  those  mills  were  very  small,  a  proof  of  which  is  to 
be  found  in  the  fact  of  ancient  heroes  using  them  as  missiles  for  throwing 
at  their  enemies  during  battle. 

A  stone  of  this  description  weighs  some  45  Ibs.,  and  does  not  exceed 
1  foot  in  diameter.  The  upper  stone,  slightly  conical,  is  4J  inches  thick. 
The  nether  one  is  flat  and  2 \  inches  thick.  Such  stones  are  disinterred  in 
Abbeville  (Picardy).  Fig.  9  shows  grindstones  belonging  to  an  age  not 

1  Pope's  translation,  p.  12,  Odyssey,  Book  VII,  11.  132,  133. 

2  Ibid.,  Book  XX,  11.  132-139, 


CHAP.    l] 


FLOUR    MILLING 


9 


distant  from  that  of  Homer  (found  in  Syria).     The  working  surfaces 
of  the  upper  and  nether  stones  are  of  conic  shape.     Later  on,  we  shall 


FIG.  9. — Millstones  of  the  Age  of  Homer. 

find  proof  that  this  mill  was  the  predecessor  of  that  of  the  Romans. 
We  ventured  the  opinion  that  the  double  stone  mill  was  invented  in 


FIG.  10. — Milling  by  the  Natives  of  Morocco. 

ancient  Egypt,  and  then  brought  into  Greece.     Indeed,  the  kind  of  mill 
described  by  Homer  is  still  used  in  Morocco. 

These  mills  are  also  in  use  in  the  Orient  and  in  China.     A  celebrated 


10 


FLOUR   MILLING 


[CHAP,  i 

traveller  and  explorer  of  the  Orient,  Journefause,  says  he  saw  a  similar 
mill  on  the  isle  of  Nicaria.  Giving  a  description  of  it,  he  tells  us  that 
the  grain  was  poured  into  an  aperture  in  the  upper  stone  and  fell  in  be- 
tween the  two  stones.  The  upper  stone  (2  feet  in  diameter)  was  made  to 
rotate  by  means  of  a  stick  fixed  into  its  edge. 

Similar  millstones  are  mentioned  by  Clark,  who  saw  them  in 
Nazareth  ;  they  were  worked  by  two  women.  One  of  them  was  turn- 
ing the  upper  stone,  taking 
the  handle  with  her  right 
hand  half  way  round,  and 
passing  the  handle  to  the 
second  woman,  who  after 
performing  the  same  mo- 
tion, returned  it  to  the  first 
from  the  other  side,  &c. 
With  their  left  hands  they 
poured  the  grain  into  the 
hole  in  the  upper  stone. 

The  Chinese  rice-mills 
are  of  the  same  con- 
struction according  to 
Staunton,  though  de- 
signed not  for  the  grinding 
of  grain,  but  for  freeing  it 
of  its  outer  cover.  He 
describes  it  in  the  follow- 
ing manner  :  "  The  rice 
is  placed  in  between  two 
flat  cylindric  stones,  which 
are  so  far  apart  that  with 
the  rotation  of  the  upper  stone  the  grain  is  but  freed  of  its  covering, 
and  not  ground." 

The  type  of  hand-mill  alluded  to  by  Moses  and  Homer  is  still  preserved 
among  the  natives  of  Morocco.  Fig.  10  is  a  photograph  of  such  a  mill, 
made  in  1908. 

But  not  only  the  semi-savage  aborigines  of  Africa  use  these  mills ;  Fig.  1 1 
shows  us  an  almost  identical  hand-mill,  with  a  few  improvements,  that  the 
"  Dukhobors  "  from  the  Caucasus  used,  before  migrating  to  America. 

The  improvements  in  this  mill,  when  compared  to  the  Morocco  one, 
consist  in  the  fixing  of  the  stones  to  a  block  hollowed  out  in  the  shape  of 


FIG.  11. — A  Hand-Millstone  Set  of  the  Caucasian 
"  Dukhobors." 


CHAP,  i]  FLOUR    MILLING  11 

a  trough.  The  hole  a,  bored  in  the  side  of  the  trough,  serves  for  discharg- 
ing the  flour. 

This  type  of  hand-mill  brings  us  to  the  end  of  the  first  period  of  milling 
technics  of  the  antique,  mainly  slave-owning  culture.  The  consumption 
of  bread  not  being  high,  there  was  no  need  for  large  production  of  it, 
and  therefore  the  milling  was  successfully  performed  by  slaves  and 
women. 

The  work  being  very  difficult,  criminals  were  condemned  to  do  it 
for  punishment. 

As  to  the  woman,  it  was  one  of  the  items  of  her  ordinary  household 
work.1 

To  this  day,  in  Mecca,  a  place  is  shown  where  Fatima,  daughter  of 
Mohammed,  worked  a  hand-mill. 


II 

TYPES  or  MILLS  DRIVEN  BY  ANIMAL  POWER 

The  new  mill,  where  mainly  animal  power  and  only  partly  human 
power  is  utilised,  appears  with  the  passing  of  flour  milling  from  the 
family,  which  only  satisfied  its  private  needs,  into  the  hands  of  the  pro- 
ducer, working  for  the  market. 

The  principle  of  grinding  the  grain  between  two  millstones  remains 
in  the  new  mill,  but  it  is  larger,  and 
has  undergone  some  modification  in 
its  construction  tending  to  reduce  the 
expenditure  of  power.  This  mill 
was  invented  at  a  later  period,  yet 
we  find  no  traces  of  it  among  the 
relics  of  antique  Egyptian,  Roman, 
and  Greek  cultures.  Only  the  latest 

J  FIG.  12.— Mill  of  the  Period  of  the  Kings 

excavations  of  Pompeii   have   given  of  Rome, 

us  pictures  of  the  improved  mill  of 

the  time  of  Roman  dominion,  as  well  as  nearly  perfectly  preserved  mill- 
stones. In  all  probability  this  type  of  mill  was  invented  by  the  Romans 
at  least  150  to  200  years  B.C. 

Fig.  12  represents  the  outer  view  of  the  mill  in  question,  and  the  same 
in  section. 

1  It  is  a  curious  fact  that  in  Little  Russia,  millet  is  still  ground  with  a  "  makogon  "  in  a 
"makitra"  (pestle  and  mortar)  to  flour,  for  preparing  "borshch"  (a  kind  of  soup),  because 
millet  meal  is  not  produced  on  our  mills, 


12 


FLOUR    MILLING 


[CHAP,  i 

The  foundation  of  the  Roman  mill  consists  of  a  cylindrical  pillow  of 
stone.  A  is  about  5  feet  in  diameter  and  1  foot  thick.  To  this  founda- 
tion is  rigidly  fixed  a  conic  stone  (the 
nether  stone—''  meta  "  )  with  the  top 
truncated  about  2  feet  in  height.  The 
cone  is  provided  with  an  iron  journal 
at  the  top.  The  revolving  upper  stone 
("catillus")  B  has  two  bell-shaped 
hollows,  thus  resembling  a  sand-glass. 

In  the  place  where  the  tops  of  the 
bells  are  joined  an  iron  cross  beam  is 
fixed,  like  a  dove-tail  in  shape  at  the 
ends. 

In  the  middle  of  this  beam  is  a 
round  hole,  into  which  the  journal 
is  inserted,  so  that  in  between  the 
inner  sides  of  the  lower  bell  and  the 

outer    surface    of   the    cone    there    is 
FIG.  13. — Roman  Mill  turned  by  a  Horse. 

just  the  space  needed  for  grinding  the 

grain  which  is  put  there.     The  grain  is  poured  into  the  hollow  C  of  the 
upper  bell  B,  acting  the  part  of  hopper,  from  whence  it  falls  into  the  space 


FIG.  14. — Roman  Mill  driven  by  Slaves  and  Asses. 

between  the  grinding  surfaces.  The  upper  stone  is  revolved  by  means 
of  levers  D,  which  are  inserted  into  the  two  or  four  rectangular  cavities 
made  in  it. 


CHAP.    I 


FLOUR   MILLING 


The  product  is  discharged  into  the  ring-shaped  groove  below,  made 
on  the  surface  of  the  foundation. 

We  have  detailed  information  concerning  the  nature  of  stones  used 


FIG.  15. — Pompeian  Mills. 

in  milling  from  Pliny.     Judging  by  his  descriptions,  it  was  known  that 
not  every  stone  can  be  used  for  milling  purposes.      The  grindstones  of 


FIG.  16.— A  Chinese  Mill. 


the  Pompeian  mills  were  shaped  of  lava  from  Vesuvius.  Coarse  and  fine 
sieves,  made  of  horse-hair  and  linen,  were  used  for  separating  the  flour 
from  the  bran  and  whole  grains  that  passed  unground.  There  were  usually 


14 


FLOUR   MILLING 


[CHAP,  i 


several  kinds  of  flour  known  on  the  market.  He  mentions  even  the 
number  of  flour  grades  and  refuse  obtained  from  one  medimnum  holding 
108  laurels,  viz.  : 

Flour  of  finest  quality  (pollen)     .          .          .          .  17  laurels. 

Flour  of  medium  quality  (similago)      .       .  .         v  50  ,, 

Flour  of  semolina,  1st  quality  (farini  tritici) .          .  30  J  ,, 

Flour  of  semolina,  2nd  quality  (secundarii  panis)  .  2|  ,, 

Flour  of  semolina,  3rd  quality  (cibarii  panis)          .  2J  ,, 

Bran  (furfur) 3 

Various  refuse  .          .           .          .          ..'.-„  2J  ,, 

Total.          .          .          ,          .       ;..          .     108  laurels. 

It  was  mentioned  above  that  working  the  mill  was  the  occupation  of 
women,  chiefly  female  slaves.     Men  were  employed  in  that  work  later 

— serfs  and  criminals, 
sometimes  forced  to 
wear  wooden  discs  round 
their  necks,  to  prevent 
any  possibility  of  reach- 
ing their  mouth  with 
the  hand  and  eating  the 
flour. 

After    it    was    dis- 


covered  that  larger  and 
heavier  stones  work 
with  greater  efficiency, 
animal  power  was  put 
to  use,  especially  that  of 
horses  and  asses. 

For  that  purpose  a 
fencing  of  beams  with 
shafts  for  the  harnes- 
sing of  horses  was  ar- 
ranged round  the  runner, 
as  shown  in  Fig.  13, 
which  represents  part 
of  a  bas-relief  in  the 
Vatican.  Blinkers  were 

placed  on  the  eyes  of  the  animals,  probably  to  prevent  giddiness. 

The  mill  driven  by  an  ass  is  reproduced  in  a  book  on  Herculaneum 

and  Pompeii,  by  Rou-Barre  (vol.  2,  tab.   83).     This  drawing  was  made 


FIG.  17.— A  Hindoo  Mill. 


CHAP.   I 


FLOUR   MILLING 


15 


from  a  picture  at  the  entrance  to  the  Pompeian  Pantheon.  Besides 
the  mill  there  are  the  mill-demons  shown  in  the  picture.1  The  mill  is 
in  the  middle  of  the  picture,  and  seven  spirits  are  seen  round  about 
it,  some  working,  others  resting  from  their  work  over  a  glass  of  wine. 
One  of  the  spirits  is  about  to  harness  an  ass  and  to  start  his  work.  Fig.  14 
shows  a  similar  mill  at  work.  Fig.  15  is  a  photograph  of  four  such  mills 
after  their  disinterment,  in  perspective.  Those  mills  were  found  close 
to  a  bakery,  and  probably  formed  a  complete  bread  factory. 

Mills  with  a  lever-drive  evidently  kept   their  place  a  long  time  in 


^H^^^l 


FIG.  18.— A  Chinese  Mill  worked  by  Buffaloes. 

milling.  They  are  to  be  met  with  in  the  classic  world  as  well  as  in  the 
far  Orient.  A  Chinese  mill,  worked  with  the  aid  of  a  horizontal  lever  by 
a  man,  is  represented  in  Fig.  16. 

Fig.  17  is  a  picture  of  a  Hindoo  mill  driven  by  oxen.  Though  it  is 
furnished  with  a  lever-drive,  the  primitive  mortar  and  pestle  system 
has  been  retained  here.  The  crushing  of  grain,  however,  is  based  on  the 
principle  of  grinding.  This  mill  was  described  by  the  traveller  Sonerat 
in  his  book,  Reise  nach  Ostindien  und  China. 

Animal  power  is  still  used  in  modern  China  for  driving  mills.  Fig.  18 
shows  a  mill  driven  by  buffaloes.  Yet  we  must  note  that  modern  Chinese 
mills,  where  buffaloes  are  employed  as  motive  power,  have  received 
considerable  improvements,  in  comparison  with  those  of  the  Romans. 

1  A  belief  that  an  unholy  power  lives  in  the  mill  exists  also  among  the  Slavs. 


FLOUR   MILLING 


[CHAP.  1 


III 

THE  UTILISATION  OF  WATER  POWER  FOR  MILLS 

As  the  construction  of  a  mill  grew  heavier,  in  response  to  the  need 
of  greater  output,  men  were  forced  to  apply  a  greater  driving  power, 
which  should  be  more  efficacious  than  the  muscles  of  a  slave,  woman,  or 


FIG.   19. — A  Water-mill  as  described  by  Vitruvius. 

animal.  Naturally,  they  turned  to  water  and  air  first  of  all,  and  utilised 
the  power  of  these  moving  elements. 

The  first  veracious  information  concerning  mills  driven  by  means  of 
under-shot  water-wheels,  and  a  minute  explanation  of  their  construction, 
we  find  in  Vitruvius.1 

It  is  to  be  regretted  that  Vitruvius  in  his  immense  work  about  the  art 
of  building  did  not  furnish  it  with  drawings  ;  all  illustrations  given 
in  some  of  the  later  editions  of  his  work,  are  only  attempts  to  depict 
what  he  described. 

1  Vitruvius,  a  Roman  architect,  wrote  De  Architectures  about  16-13  years  B.C. 


CHAP.    l] 


FLOUR    MILLING 


17 


Such  is  the  drawing  in  Fig.  19,  taken  from  an  edition  of  Vitruvius' 
work,  published  in  1521  in  Camo,  in  Old  Italian. 

Here  A  represents  a  wooden  water-wheel.  On  its  rim  are  radially- 
fixed  paddles  B,  receiving  the  pressure  of  moving  water,  and  boxes  or 
ladles  C,  which  serve  to  bring  up  the  water  used  for  special  purposes.1 
The  shaft  of  the  water-wheel  is  turned  with  the  long  end  inwards.  On 
the  square  part  of  the  shaft  D  is  fixed  a  comb-wheel  E  engaged  with  a 
mangle  gear.  The  cogs  of  the  collar  comb-wheel  enter  into  the  mangle 
wheel  F,  set  on  G,  the  spindle  of  the  millstone,  which  rests  with  its  lower 
end  on  a  beam  L,  the  upper  end  passing  through  a  fixed  (not  shown  in  the 
drawing)  lower  grindstone,  and  is  hermetically  fastened  to  the  runner  H, 
into  the  opening  of  which  the  product  to  be  ground  is  poured.  The  latter 
is  fed  from  a  pyramidal 
hopper  K,  where  the 
grain  is  kept.  The  lower 
opening  of  the  hopper 
is  furnished  with  an  ad- 
justable vibrating  shoe. 

The  water  lifted  by 
the  wheel  A  pours  out 
of  the  boxes  G  into  a 
tank  R,  whence  through 

an  Opening  X  it  passes  FIG.  20.— Arabian  Water-mill. 

into  the  spout   7,  and 

may  be  used  for  irrigation.  Possibly  a  fullery  was  attached  to  the  mill, 
which  may  explain  the  presence  of  a  hammer  0  in  the  drawing,  though 
it  may  have  been  used  for  hammering  a  stopper  into  the  outlet  X. 

We  may  suppose  the  use  of  horizontal  water-wheels  or  turbines  on 
mills  to  be  nearly  as  old  as  the  use  of  vertical  water-wheels.  Simple 
turbines  are  found  in  mountainous  regions  in  almost  all  lands  where  the 
population  is  slightly  touched  by  civilisation,  however  low  their  mechanics 
may  stand. 

Fig.  20  proves  this  surmise  to  be  correct.  It  is  a  drawing  of  an 
Arabian  water-mill,  made  at  Rollet's  by  a  captain  of  the  French  artillery 
soon  after  the  taking  of  Constantinople  by  the  French.  A  denotes  the 
wall  of  the  mill-building,  B  the  hopper  for  pouring  the  grain  in,  C  a  cross 
bar  communicating  a  vibratory  motion  to  the  hopper,  D  a  revolving 
grindstone  (making  112  revolutions  in  the  present  case),  E  the  spindle  of 
the  grindstone,  F  masonry  serving  as  nether  stone  at  the  same  time, 

i  Probably  for  irrigation. 


18  FLOUR   MILLING  [CHAP,  i 

G  a  cavity,  where  the  ground  product  (flour  semolina)  is  collected,  H  a 
shaft  on  which  a  turbine  I  is  mounted,  K  a  ladder,  L  a  lever  for  the  runner 
D,  M  a  gate  in  front  of  the  spout  N.  It  is  also  mentioned  that  the 
turbine  is  1'6  metres  in  diameter,  and  is  furnished  with  thirty 
paddles. 

With  the  aid  of  a  spout,  through  a  small  opening  in  the  dam,  the 
water  is  directed  on  to  one  half  of  that  wheel,  so  that  it  falls  into  the 
concave  side  of  the  paddles  bringing  the  wheel,  the  shaft  H,  and  grinder  D 
into  motion. 

As  to  horizontal  water-wheels  in  the  mills,  M.  Riihlmann  quotes  an 
extract  from  the  French  encyclopaedia. 

In  the  14th  vol.  of  the  Dictionnaire  Technologique,  p.  207,  it  is  stated 
that  horizontal  water-wheels  in  the  so-called  bazacle  mills  in  Tumra 
were  built  in  the  twelfth  century  (1190). 

Then,  in  the  issue  of  Neues  Hannoversches  Magasin  on  Oc- 
tober 4,  1802,  p.  1277,  is  the  following  description  of  a  Bashkir 
mill  that  was  evidently  a  contemporary  of  the  vessel  mills  of 
Belisarius : 

"  The  Bashkirs  have  mills  of  a  peculiar  construction,  apparently  an 
invention  of  the  people.  With  the  view  of  economising  labour,  they 
choose  the  smallest  rivulets  for  their  mills,  make  a  hedge  of  twigs  which  is 
filled  with  earth,  and  dam  the  stream  with  it  (or  an  ordinary  dyke  of 
brushwood).  On  the  dyke  is  built  a  hut  on  piles.  In  that  hut  grindstones 
are  placed  on  a  scaffolding  standing  in  the  middle  with  railings  running 
round  its  edge.  The  grinders  are  not  of  stone,  but  of  a  hard  tree  stump 
or  block  of  wood;  and  are  shaped  in  the  form  of  plates,  studded  in  an 
orderless  way  with  flat  iron  nails,  so  laid  that  their  prominent  parts  run 
lengthways  from  the  centre  to  the  periphery.  The  nether  wooden 
grinder  is  rigidly  attached  to  the  scaffolding,  while  the  'upper  one  may  be 
raised  and  revolves  conjointly  with  the  vertical  shaft  that  runs  through 
the  opening  in  the  nether  grinder  and  rests  with  the  point  of  an  iron 
crutch  in  a  cavity  made  in  the  centre  of  the  upper  grinder.  The  vertical 
shaft  is  usually  made  of  one  block  of  wood,  so  that  its  lower  part  ends  in 
a  round  thick  knob,  into  which  a  good  number  of  flat  wings  or  paddles, 
slightly  concave  on  one  side,  may  be  hammered  in  a  manner  resembling 
the  spokes  in  a  wheel,  and  forming  the  water-wheel  proper.  A  bolt  is 
hammered  into  the  thick  end  of  the  shaft  below,  by  means  of  which  the 
vertical  shaft  rests  in  the  rivulet  on  a  beam  and  revolves  in  it,  as  in  a 
bearing. 

"  The  grain  to  be  ground  into  semolina  or  coarse  flo,ur  is  ppure$ 


CHAP.    I] 


FLOUR    MILLING 


19 


into  a  hopper  built  of  planks.  Under  the  opening  of  that  hopper,  a  short 
horizontal  spout  is  placed,  leading  to  the  opening  in  the  middle  of  the 
upper  grinding  disk.  The  corn-bin  with  grain  is  hung  to  the  cross-beam 
of  the  mill,  free  to  be  shifted.  A  handle,  tied  %to  the  corn-bin,  which 
touches  the  upper  grinder  with  one  end,  imparts  a  vibrating  motion 
to  it." 

We  presume,  however,  that  the  author  errs  in  ascribing  the  inven- 


FIG.  21. 

tion  of  this  mill,  with  a  horizontal  water-wheel,  to  the  Bashkirs.  From 
the  oldest  times  and  up  to  this  day,  such  a  mill  is  a  common  object  in 
the  Caucasus.  Possibly  the  author  has  mistaken  the  natives  of  Caucasus 
for  Bashkirs. 

The  mountaineers,  and  even  the  people  of  the  plains  of  the  northern 
Caucasus,  chiefly  use  maize  flour,  of  which  an  unleavened  bread  is  pre- 
pared, "Chureck."  Wheat  is  also  ground,  but  is  used  only  with  an 


20 


FLOUR   MILLING 


[CHAP,  i 


admixture  of  maize  flour,  as  the  use  of  pure  wheat  flour  is  a  luxury  among 
the  natives.     The  whole  amount  of  maize  and  wheat  is  ground  for  local 


FIG.  22. — A  Caucasian  Mill  with  one  Set  of  Grinders. 

consumption  in  the  water-mills  depicted  in  1802  by  the  Neues  Hanno- 
ver sches  Magasin. 

Pig.  21  is  a  sketch  of  this  mill.     The  shaft  of  a  horizontal  water- 
wheel  rests  with  one  end  e  on  a  step-bearing  in  the  shaft  d,  which  may  rise 


CHAP.   I 


FLOUR    MILLING 


21 


and  fall  with  the  aid  of  a  stem  /  and  a  wedge  in  its  upper  end.  To  the 
upper  end  of  the  shaft  is  fixed  a  runner  by  means  of  a  driving  iron  a.  On 
the  lower  end  of  the  shaft  is  set  a  wooden  hub  furnished  with  ten  to 
twelve  paddles. 

The  number  of  revolutions  of  the  water-wheel  is  from  forty  to  eighty 
per  minute,  the  fall  of  the  water  being  3J  to  7  feet.  The  diameter  of  the 
grinders  is  Ij  to  3|  feet,  the  thickness  3j  to  7  inches. 


FIG.  23. — A  Caucasian  Mill  with  three  Sets  of  Grinders. 

These  mills  are  usually  furnished  with  one  burr,  and  are  built  on 
mountain  brooks.  Their  capacity  varies  from  1  to  8  or  10  poods  l  per  day. 

Fig.  22  is  a  photograph  of  such  a  mill,  with  a  single  set  of  grinders. 
It  is  of  brushwood  wicker-work,  with  a  thatched  roof.  Fig.  23  shows  a 
mill  with  three  sets  of  grinders,  and  lastly,  Fig.  24  gives  us  a  view  of  nine 
such  mills,  situated  along  a  mountain  torrent,  clinging  to  the  mountain 
side  like  swallow  nests. 

i  lpood  =  361bs. 


22 


FLOUR   MILLING 


[CHAP.  I 

In  these  mills  the  work  is  usually  performed  by  women.     This  type 
of  water-wheel  became   known   in    France   and   Germany  only  in  the 


FIG.  24. — A  Row  of  Mills  along  a  Mountain  River. 

fifteenth  century.  Therefore,  the  supposition  that  these  mills  were 
brought  to  Europe  by  the  crusaders  at  the  end  of  the  thirteenth 
century  is  quite  just. 


CHAP,  i]  FLOUR   MILLING  23 

IV 

THE  AMERICAN  AUTOMATIC  MILL 

A  strong  impetus  was  given  to  the  development  of  milling  technics 
in  Europe  by  the  Americans.  The  idea  of  an  automatic  mill,  as  of  many 
other  improvements  in  machines  connected  with  the  principle  of  auto- 
matism, belongs  to  them. 

It  is  astonishing,  but  a  fact  nevertheless,  that  the  discovery  of  the 
French  quarry  "  La  Ferte-sous-Jouarre,"  producing  the  famous  French 
stones,  was  made  by  the  Americans.  That  stone  was  used  in  America  for 
making  grinders  a  long  time  before  it  became  known  to  the  French  millers. 

The  Americans  threw  away  the  sifting  bag  of  the  old  European  mill, 
and  substituted  for  it  cylindrical  and  polygonal  reel-separators,  which 
are  also  American  inventions.  For  the  transportation  of  the  product 
the  Americans  adapted  elevators  and  conveyors.  For  the  cooling  of 
flour  special  apparatus  called  hopperboys  were  planned.  The  flaxen 
tissue  in  sifting  bags  was  supplanted  first  by  wool,  then  by  wire,  and  lastly 
by  silken  tissue. 

Thus  everything  tending  to  progress  in  the  technics  of  the  furnishing 
of  mills  in  the  end  of  the  eighteenth  and  first  quarter  of  the  nineteenth 
centuries  belongs  to  the  initiative  of  the  Americans.  For  nearly  forty 
years,  up  to  the  thirties  of  last  century,  the  teacher  of  the  Europeans 
was  the  celebrated  American  engineer,  Oliver  Evans,  whose  book  has 
passed  into  thirteen  editions,1  and  was  translated  into  French  and  German. 

In  the  review  of  European  mill  building  the  great  influence  of  America 
on  Europe  in  that  respect  will  be  pointed  out.  At  present,  we  shall  give 
a  description  of  a  typical  American  automatic  mill,  the  design  of  which 
was  completed  by  Evans  as  early  as  1783. 

Fig.  25  illustrates  the  whole  process  of  milling  in  a  longitudinal 
section  of  Evans'  mill  (Evans'  automatic  mill). 

The  mill  is  situated  on  a  river.  The  reception  of  the  grain  is  effected 
either  by  means  of  an  elevator  from  a  vessel,  or  from  carts  brought 
up  to  the  mill.  We  shall  first  examine  the  reception  from  carts. 

The  grain  is  poured  out  of  sacks  down  spout  1  on  to  a  scale  2.  After 
being  weighed  it  is  let  down  into  the  grain  bin  3  (black  pit),  and  thence 
through  spout  t  conducted  to  the  elevator  4-5,  which  supplies  the  large 
bin  6.  Part  of  the  floor  below  6  is  also  occupied  by  bins,  ending  in  a 

1  Oliver  Evans,  The  Young  Millwright  and  Miller's  Guide,  the  thirteenth  and  last  edition 
published  in  Philadelphia,  1850. 


24 


FLOUR   MILLING 


[CHAP.  1 


pyramidal  bin  7,  on  the  next  floor  but  one  below.  Out  of  bin  7  the  grain 
passes  through  the  hopper  8  into  the  burr,  the  purpose  of  which  is  to  rub 
off  the  outer  husk,  remove  the  germ  and  dirt.  Consequently  this  grinder 
is  the  same  as  the  German  Spitzgang.  The  grain,  comparatively  cleaned 
of  husk,  germ,  and  dirt,  is  aspirated  in  passing  out  of  the  grinder,  the 
clean  grain  falling  again  into  bin  3  (no  dirty  grain  is  mixed  with  it,  as  it- 
was  all  passed  into  bin  6),  the  heavy  refuse  into  bin  9  lying  below,  while 


FIG.  25. 

the  air  and  light  refuse  are  blown  out  through  an  opening  in  the  bin  9a. 
In  proportion  to  the  freeing  of  the  grain  of  its  husk,  it  is  taken  by  the 
same  elevator  4-5,  this  time  into  bins  10  and  11.  From  these  bins  it  is 
conveyed  into  the  reel- separator  12,  where  the  small  grain  and  chaff  are 
sifted  away.  The  throughs  of  that  separator  are  fanned,  therefore  the 
good  grain  falls  into  bin  14,  the  light  kernels  and  chaff  are  blown  by  the 
ventilator  into  bin  32,  and  still  lighter  refuse  into  bin  33. 

Out  of  bin  14  the  cleaned  grain  passes  into  conveyor  15-16  with  paddles 
right  and  left,  which  discharges  the  grain  into  conveyor  boxes  17,  7,  18, 
which  feed  the  grinders  8,  19,  20. 


CHAP,  i]  FLOUR   MILLING  25 

After  the  grinding  the  product  is  conducted  into  the  common  con- 
veyor 21-22  and  then  into  elevator  23-24,  which  passes  it  into  the  hopper- 
boy  25,  a  kind  of  flour  mixer  designed  by  the  Americans  for  the  purpose 
of  cooling  the  product.  On  leaving  the  hopperboy,  the  flour  flows  first 
on  to  two  cylindrical  reel-separators  26,  where  the  throughs  are  conveyed 
into  bins  28  and  29  with  a  chamber  for  flour,  and  the  refuse  left  on  them 
is  once  more  sifted  on  the  controlling  separator  27.  The  refuse  from 
separator  27  is  taken  by  conveyor  31  either  to  bin  32  to  the  light  kernels 
and  chaff,  and  then  reground  on  grinder  8,  or  ground  apart. 

Thus  we  have  a  complete  automaton,  with  grain-cleaning  and  repeated 
grinding  of  the  product,  if  needed. 

The  principle  of  sorting  the  product  according  to  quality  was  known 
to  Americans  long  before  the  Europeans  learned  of  it,  and  effected  with 
much  greater  success.  It  is  ne- 
cessary to  describe  the  sorting 
cylinder  12,  where  the  coarse  im- 
purities as  well  as  chaff  or  small 
grains  are  sorted  away  (Fig.  26). 

This  cylindrical  reel-separator 
is  an  invention  of  Evans  (called 
"  Rolling  Screen  and  Fan  "),  and 
works  in  the  following  manner  :  FIG  26. 

out  of  the   conveyor   box  r   the 

grain  flows  into  the  inner  cylinder  b  concentric  to  cy Under  a.  The 
meshes  in  the  cloth  of  cylinder  a  are  smaller  than  the  grain,  those  of 
cylinder  b  larger.  The  two  sieves  are  joined  to  each  other.  The  refuse 
of  sieve  6,  large  admixtures,  passes  into  box  e,  the  throughs  into  sieve  a. 
The  refuse  of  sieve  a,  the  good  grain,  flows  into  bin  k,  and  the  throughs, 
fine  dust,  &c. .  fall  through  a  crevice  in  the  air-pipe.  The  grain  and  throughs 
are  subjected  to  the  effect  of  a  current  of  air  blown  by  fan  g  along  /. 
The  dust  is  carried  out  and  the  heavy  refuse  falls  into  bins  i  and  h. 

The  diameters  of  these  cylinders  are  2,  5,  and  3  feet ;  the  number  of 
revolutions  15  to  18  per  minute. 

When  the  mill  is  supplied  with  grain  from  a  barge  or  vessel,  the  re- 
ception is  accomplished  by  an  elevator,  39,  which  ascends  and  descends 
with  the  aid  of  chain  sheaves  42-43.  The  elevator  pours  the  grain  into 
the  conveyor  45,  which  carries  it  into  bins  10  and  11,  the  conveyor  being 
exhausted  the  while.  The  dusty  air  is  discharged  out  of  the  conveyor 
45  on  its  left  side,  and  out  of  the  grain-cleaning  chamber  of  the  mill 
through  the  outlet  Q. 


26  FLOUR   MILLING  [CHAP.  1 

V 

THE  INFLUENCE  OF  AMERICAN  TECHNICS  IN  EUROPE 

In  the  civilised  countries  of  Western  Europe  for  many  centuries  the 
system  of  a  single  milling  passage  reigned,  and  is  still  adhered  to,  in 
peasant  windmills.  In  those  mills  both  grain  and  husks  were  ground 
in  millstones,  and  the  flour  was  sifted  through  hand-sieves  of  horsehair 
preparatory  to  baking.  Some  250  years  ago  the  sifting  bag  was  adapted 
to  the  mill  and  performed  the  work  of  a  sifting  apparatus. 

Over  150  years  have  elapsed  since  the  French  technics  introduced  a 
new  style  of  milling — the  repeating  type  (mouture  economique),  which 
is  beginning  slowly  to  spread  in  Europe. 

Up  to  the  end  of  the  eighteenth  century  the  milling  technics  of  Europe 
remained  the  same  with  scarcely  any  alterations,  there  being  no  motive 
cause  for  progress,  either  in  social  organisation  or  in  the  trade- corpora- 
tion industry.  Flour  mills  were  working  almost  exclusively  to  supply 
local  needs,  and  seldom  for  neighbouring  districts. 

The  last  quarter  of  the  eighteenth  century  witnessed  the  beginning 
of  the  gigantic  breaking  up  of  the  economic  structure  of  feudal  Europe, 
caused  by  three  powerful  historical  factors,  which  brought  about  a  new 
era  of  progress.  Those  factors  were  :  the  perfecting  of  Watt's  steam- 
engine,  the  struggle  for  liberty  in  America,  and  the  French  Revolution. 
Technical  progress  and  the  victory  of  the  middle-class  over  the  feudal 
system  in  Europe  rendered  possible  the  organisation  of  industry  on  new 
principles  of  production,  those  of  capital. 

The  first  country  benefited  by  the  principle  of  capitalism  in  the  flour- 
milling  sphere  was  America,  as  the  production  of  flour  in  the  United  States 
required  a  great  number  of  mills.  The  want  of  hands  and  the  high  wages 
forced  the  Americans  to  have  recourse  to  a  rational  technical  organisation 
of  production. 

To  that  end,  in  the  beginning  of  the  nineteenth  century  hundreds 
of  automatic  mills,  similar  to  the  one  described,  were  built  in 
America,  chiefly  in  the  state  of  Pennsylvania  and  along  the  river 
Mississippi. 

The  influence  of  American  milling  technics  became  noticeable  first 
in  the  English  milling  industry,  partly  by  reason  of  their  economic  relations, 
which  were  closer  between  these  two  countries  than  between  the  others, 
partly  owing  to  their  common  tongue.  Yet  that  influence  commenced 
only  after  1781,  as  is  proved  by  the  fact  that  the  most  reliable  English 


CHAP,  i]  FLOUR   MILLING  27 

work  of  the  time  (Bees'  Cyclopcedia)  in  its  chapter  on  flour  milling  *  gives 
a  detailed  description  of  English  mills,  in  which  no  mill  of  American  type 
is  mentioned.  It  also  speaks  of  a  celebrated  English  engineer,  Smitton, 
who  built  in  1781,  in  Deptford,  a  mill  for  the  needs  of  the  fleet,  called  by 
him  "  The  Steam  Mill,"  according  to  his  own  system  that  he  had  worked 
out  as  early  as  1754.  The  motor  adapted  by  Smitton  was  Newcomen's 
steam  pump,  which  pumped  water  into  tanks,  placed  at  a  sufficient  height. 

The  water,  flowing  from  these  tanks  on  to  the  water-wheels,  worked 
the  mill. 

At  the  end  of  1782,  Watt  had  so  far  perfected  his  steam-engine,  that 
it  was  possible  to  adapt  it  for  immediate  use  in  working  a  factory.  In 
1785  was  built  the  first  steam-mill  in  London  close  to  Blackfriars'  Bridge, 
which  was  called  Albion  Mills.  It  was  built  and  arranged  by  the  engineer 
John  Rennie,  and  the  Watt's  steam-engine  was  purveyed  by  the  works  of 
Boulton  &  Watt,  in  Soho.  The  mill  only  began  operating  in  1786,  having 
ten  millstones  for  wheat  grinding. 

The  capacity  of  the  steam-engine  was  50  h.p.,  1  h.p.  grinding  63  Ibs. 
of  wheat  per  hour,  and  burning  about  3|  cwt.  of  coal  per  hour !  But 
even  that  great  expenditure  of  fuel  was  considered  to  be  very  profitable, 
and,  judging  by  the  results  of  milling,  Rennie's  mill  was  recognised  to 
be  exemplary. 

During  the  end  of  the  eighteenth  century,  mill-building  in  England 
made  rapid  progress.  Besides  the  brothers  Rennie  (George  and  John), 
in  that  department,  the  names  of  Modsley,  Etken,  and  Steel  in  London, 
Fenton,  Murrey,  and  Woods  in  Leeds,  and  Fairbairn  and  Lille  in  Man- 
chester are  renowned. 

George  and  John  Rennie  built  a  mill,  the  largest  in  the  world2  at 
the  time,  in  Plymouth,  for  the  victualling  of  the  fleet,  containing  twenty- 
four  millstone  sets.  This  was  probably  the  first  fireproof  mill,  as  the 
building  was  constructed  of  iron  and  stone.  The  millstone  sets  were 
divided  into  four  groups,  each  group  of  six  being  driven  by  one  large 
cogged  wheel. 

VI 
MILLS    IN   FRANCE  • 

Flour  milling  in  France  of  the  eighteenth  century  was  far  superior 
that  in  other  European  countries.     In  a  book  by  Malouins,  published 
in  1767,  we  find  the  description  of  a  mill  where  the  product  was  twice 

1  Rees'  Cyclopcsdia,  vol.  xxiii.,  1781.  2  Ibid. 


28 


FLOUR   MILLING 


[CHAP.  I 


sifted  by  means  of  reel- separators.  Fig.  27  is  a  rather  primitive,  but 
sufficiently  characteristic  drawing  of  the  inner  arrangement  of  the  mill. 

The  millstone  set  GK  rests  on  a  timber  bursting  M.  The  feed- 
hopper  B  is  filled  with  grain  by  a  workman.  The  float  D  in  the  feed  is 
a  sufficiently  heavy  plank  attached  by  a  string  C  to  the  bell  E.  When 
the  grain  is  spent  and  the  hopper  is  empty,  the  falling  plank  D  pulls 
the  string,  and  rings  the  bell  as  a  signal. 

A  large  wooden  box  L  and  two  separators  K-K  are  placed  under  the 


FIG.  27. 

bursting.  The  ground  product  flows  into  the  upper  separator  or  dresser. 
The  refuse  from  that  separator  passes  on  into  the  lower  one. 

The  throughs  of  the  separators  yielded  flour  which  was  collected  in 
the  box  L. 

To  prevent  the  flour  from  escaping  into  the  building,  the  box  and 
separators  were  hooded  with  a  curtain  which  formed  a  kind  of  dust 
chamber.  The  tissue*  in  the  separators  was  woollen. 

In  proportion  to  the  flour  collected  in  the  box  the  curtain  was  lifted 
and  the  flour  removed  with  shovels. 


CHAP,  i]  FLOUR    MILLING  29 

The  influence  of  American  milling  technics  began  to  penetrate  into 
France  much  later  than  into  England.  In  the  celebrated  Methodical 
Encyclopedia  of  Diderot  and  D'Alambert  (1788),  a  mill  of  the  end  of 
the  eighteenth  century  is  described  greatly  resembling  the  type  of  mills 
constructed  in  the  beginning  of  that  century,  depicted  by  Belidor  in  a 
work  called  Architecture  Hydrolique,  as  early  as  1737. 

Such  stagnancy  in  milling  technics  and  industrial  life  generally  has 
its  explanation  in  the  stormy  period  of  the  French  Revolution  and  in  the 
wars  of  the  succeeding  Empire.  Only  after  the  continental  wars  had 
ended  did  the  industry  of  France  revive,  and  flour  milling  adopt  the 
Anglo-American  type  of  mills.  These  new  types  of  mills  in  France  were 
built  by  English  fmns.  In  1818  the  English  engineer,  Modesley,  was 
building  a  mill  of  four  millstone  sets  in  St.  Quentin.  In  1825  Atkins 
and  Steel  built  a  mill  in  St.  Denis,  near  Paris,  for  Bensit,  who  acquired 
a  name  in  the  French  milling  literature  later. 

But  the  vivacious  and  creative  mind  of  the  French  was  not  satisfied 
in  the  further  development  of  mill-building  with  imitating  the  English 
and  Americans.  French  engineers  have  introduced  many  original  inven- 
tions, chiefly  in  the  sphere  of  transportation,  cleaning  of  grain/and  dress- 
ing the  product.  The  building  of  their  mills  excelled  in  beauty  of  archi- 
tecture, and  the  departments  in  proportionality  of  sizes.  One  of  the 
greatest  inventions  of  the  French  of  that  time  is  the  cleaner  and 
separator,  the  most  indispensable  machine  of  the  grain-cleaning  de- 
partment. Doubtless  the  development  of  milling  technics  pushed  the 
question  of  perfecting  the  water-wheel,  adapted  then  almost  exclusively 
in  mills,  to  the  front,  and  it  was  Fourneyrond  who  produced  the  first 
turbine.  This  was  of  no  less  importance  to  the  development  of  milling 
in  France  than  was  Watt's  steam-engine  in  England. 

VII 

PROGRESS  OF  TECHNICS  IN  GERMANY 

The  old  German  mill  which  was  in  use  up  to  the  fifties  of  the  nine- 
teenth century  l  is  illustrated  in  Fig.  28.     Such  mills  (section  in  Fig.  28  A) 
were  driven  by  a  water-wheel  with  the  aid  of  a  mangle  gearing  m-l. 
The  mangle  gear  I  is  set  on  a  spindle  resting  on  the  step-bearing  K 
dng  on  a  beam  p  which  may  be  raised  and  lowered,  regulating  the 
Listance  between  the  grinding  surfaces.     The  adjustable  grinder  B  is  con- 
lected  with  the  spindle  by  a  driving  iron  i.     Fig.  28  B  gives  the  side  view, 

1  Prechtl,  Technologische  Encyclopadie,  vol.  x.     Stutthard,  1840, 


30  FLOUR    MILLING  [CHAP,  i 

From  the  millstone  the  flour  flows  into  a  woollen  sifting  bag  K,  to 
which  a  vibratory  motion  is  communicated  by  a  fork  v,  performing 
returning  oscillations  from  shaft  vr  The  fine  flour,  sifted  through  the 
bag  K,  passes  into  the  box  L.  The  bran,  semolina,  and  coarse  meal 
(overtails)  fall  on  sieve  M,  where  the  bolting  is  repeated.  In  this  manner, 
two  kinds  of  flour  were  obtainable,  and  semolina,  which  was  then  reground. 
Sometimes  the  sifting  bag  was  replaced  by  sieves  of  different  density,  to 
obtain  a  greater  number  of  kinds  of  flour.  C  is  a  solid  driving  iron. 
D  a  ratchet  wheel  for  the  vibratory  motion  of  the  shoe  set  into  the 
opening  of  the  runner  (see  A)  ;  Fig.  E,  a  mechanism  communicating  the 
vibratory  motion  to  the  fork  v  which  shakes  the  sifting  bag.  The 
mechanism  shown  in  Fig.  F,  and  the  working  of  which  is  obvious,  was 
frequently  adapted  for  the  same  purpose.  In  the  first  and  second  case 
the  revolving  cross-head  w  acting  upon  a  wooden  spring  v2  effects  a 
vibration  of  the  rollers  on  which  the  spring  is  set.  Fig.  G  is  a  sieve  M 
for  sifting  the  overtails  from  the  sifting  bag ;  Fig.  H  is  a  wooden  spring 
counterbalancing  the  vibrations  of  the  sieve  M .  The  tightening  of  the 
spring  is  regulated  either  by  transposing  the  taper-pin  i,  or  tightening 
the  string  s.  On  Figs.  K  and  N  we  find  the  shaft  and  screw  apparatus 
for  raising  the  vertical  journal  p  when  the  distance  between  the  grinding 
surfaces  is  to  be  regulated. 

The  new  mill  made  its  appearance  in  Germany  later  than  in  England 
and  France.  The  feudal  system,  the  corporate  organisation  of  the 
trades,  and  the  conservatism  in  technics  maintained  by  them  were  the 
chief  causes  of  this  tardiness. 

The  feudal  law  had  created  the  so-called  "  compulsory  grinding  " 
in  the  mills  belonging  to  the  landowner,  thus  putting  the  monopoly  of 
production  into  the  hands  of  the  lord  of  the  manor,  and  precluding 
any  possible  competition.  Yet  the  necessity  of  competing  in  the  market 
and  fighting  against  the  imported  French  and  English  flour  forced  the 
Germans  to  adopt  the  American  type  of  mill,  as  more  efficient  and  pro- 
ducing better  flour. 

Having  grasped  the  advantages  of  the  American  mill,  the  German 
engineers  and  industrial  promoters  commenced  studying  that  type  with 
the  carefulness  and  minuteness  characteristic  of  the  nation. 

The  first  German  flour  mills  of  the  Anglo-American  type  were  built 
and  began  operating  in  Prussia.  As  early  as  in  1825,  such  a  mill  was 
arranged  in  Magdeburg  by  F.  Murrey  of  Leeds;  in  Guben,  under  the 
supervision  of  an  enterprising  leaseholder,  Korti. 

Jn  Berlin  there  sprang  into  existence  a  steam-mill  of  Schuhmann 


CHAP.    l] 


FLOUR    MILLING 


31 


FIG.  29. 


32  FLOUR   MILLING  [CHAP,  i 

and  Kratzeke  arranged  by  an  engine-builder  Freund  after  the  fashion  of 
English  mills ;  and  on  the  upper  Oder  a  steam-mill  of  the  American 
type,  similar  to  that  in  Guben,  was  working. 

The  Prussian  trade  committee  furthered  these  beginnings  in  every 
way,  by  publishing,  for  instance,  in  1825  detailed  drawings  and  descrip- 
tions of  the  best  English  and  American  mills,  and  sending  in  1827  two 
pupils  of  the  Imperial  Trade  Institute  (Hantzel  and  Wulf),  who  were 
studying  mill  building,  to  America  and  England,  to  acquire  practical 
knowledge  in  everything  pertaining  to  the  question.  Hantzel  and 
Wulf's  report  was  published  by  order  of  the  Prussian  Government  of 
1832,  and  these  two  builders  erected  with  great  success  several  large 
mills  and  very  skilfully  performed  the  milling  operations. 

In  the  western  provinces  of  Prussia  the  Ober-President  von  Winke 
became  renowned,  having  built  about  1830  the  first  standard  mill  of  the 
American  type  on  the  river  Leine. 

In  the  south  of  Germany  the  first  to  introduce  mills  of  American  con- 
struction was  the  Royal  Government  of  Wurtemberg.  The  first  mill  of 
that  type  was  erected  on  the  site  of  an  old  mill  belonging  to  the  treasury 
in  Berg,  by  Stutthart. 

The  building  of  that  mill  was  begun  in  the  summer  1830,  and  ended 
in  1831.  It  commenced  operating  on  the  1st  September  1831.  Here  three 
water-wheels  set  into  motion  ten  millstones,  three  aspirators  and  three 
separators  with  silk  cloth,  one  sieve,  two  product  elevators,  one  sorting 
dresser,  and  several  sifting  machines.  In  a  short  time  the  flour  from 
this  mill  commanded  so  extensive  a  market  that  by  1832  an  en- 
largement of  the  mill  was  thought  of.  But  the  greatest  good  the  mill 
wrought,  was  the  example  it  set,  for  soon  in  different  parts  of  the 
kingdom  mills  of  the  Berg  type  sprang  up.  Such  mills  were  erected 
in  Althausen,  Zeflingen,  'Urach,  Reutlingen,  Tubingen,  Esslingen,  and 
Heilbronn. 

Some  time  before  the  mill  in  Berg  was  built,  the  attention  of  the  Royal 
Government  of  Bavaria  was  attracted  to  the  question,  and  it  published 
on  27th  February  1828  the  following  announcement : 

"  A  remuneration  of  3000  guldens  will  be  allotted  to  the  man,  who  in 
two  years'  time  shall  have  built  and  commenced  working  a  flour-grinding 
mill  of  at  least  three  stones,  constructed  after  the  manner  of  those  suc- 
cessfully operating  for  several  years,  in  England  and  North  America." 

The  sole  claimant  of  that  prize,a  mechanic,  Spat  of  Nurnberg,announced 
in  1831  that  a  mill  of  the  type  mentioned,  containing  four  millstones  and 
driven  by  an  overshot  water-wheel,  had  been  erected  by  him,  and  was 


CHAP,  i]  FLOUR   MILLING  33 

working.  Spat  was  awarded  the  prize  in  1832,  notice  being  taken  of  the 
fact  that  "  the  mill  is  indeed  of  the  Anglo-American  type,  but  somewhat 
modified." 

This  improved  mill  of  Spat's  enjoyed  no  great  success  as  an  example 
to  be  imitated,  and  in  1837  a  miller,  Bachmann,  was  sent  by  royal  order 
for  the  Bavarian  Millers'  Union  to  Wiirtemberg  to  study  the  American 
mills  of  that  country. 

A  far  larger  field  was  gained  by  the  Anglo-American  mills  in  the 
following  years  (1833-35)  in  Prussia,  where  the  Royal  Sea  Trading  Society 
took  a  prominent  part  in  their  diffusion. 

From  1822  that  Society,  acting  on  behalf  of  the  merchants  of  Dantzig, 
distributed  the  grain  purchased  by  it  among  the  local  mills  and  sent  the 
fine  flour  partly  to  England,  partly  to  Transatlantic  ports.  Thereby  the 
traders  soon  arrived  at  the  conclusion  that  German  flour  milling  was  too  far 
behind  that  of  foreign  countries,  particularly  of  North  America,  to  enable 
them  to  compete  successfully  on  the  outland  markets. 

In  consequence,  the  Society  purchased  a  milling  plant  situated  on 
the  Oder  in  Tiergarten,  in  the  neighbourhood  of  Ohlan  (in  Silesia),  and 
entrusted  its  reconstruction  in  the  American  fashion  to  an  experienced 
technical  miller  named  Hantzel.  In  1834  eight  stones  of  the  rebuilt 
mill  were  installed  and  started,  two  more  flaking  mills  being  added  to  the 
number  later  on. 

This  mill  was  the  standard  for  mills  built  in  after  years,  and  produced 
flour  of  a  higher  quality  for  home  use,  as  well  as  for  export. 

At  the  same  time  private  industry  did  not  remain  inactive.  Par- 
ticular attention  must  be  called  to  the  effort  of  a  merchant,  Witt  by  name, 
who  greatly  assisted  the  development  of  the  flour-milling  industry  in 
Dantzig.  In  a  mill  with  twenty  pairs  of  stones,  rented  by  him  in  Dantzig, 
he  had  twelve  reconstructed,  on  the  American  system,  and  added  new 
ones  to  them,  so  that  in  a  short  time  he  had  no  less  than  thirty-one 
millstone  sets  of  perfected  construction  in  operation. 

The  second  of  the  above-mentioned  engineers  who  had  been  sent  to 
America,  Wulf,  had  an  open  field  here  for  developing  his  activity  on  a 
large  scale  in  the  capacity  of  director  of  the  technical  side  of  the  business. 

Biischer  of  Neustadt-Eberswalde  next  deserves  mention.  He  was  a 
government  engineer,  and  with  his  five-stones  mills  of  the  American 
type  strove  to  enable  the  owners  of  small  mills,  without  any  marked 
alterations  to  the  plants,  to  produce  flour  which  only  slightly  differed  in 
quality  from  the  product  of  the  most  perfect  mills  of  the  day. 

In  1835,  Kriickmann,  the  owner  of  a  mill  in  Berlin,   adapted  his 


34  FLOUR    MILLING  [CHAP,  i 

three-stones  mill  for  hard  grain,  and  shortly  afterwards  a  councillor  of 
commerce,  Grunau  in  Elbing,  reconstructed  his  mill  in  the  improved 
style. 

Before  that,  on  the  Rhine,  opposite  to  the  town  Neuwied,  on  an  estate, 
"'  Zur  Nette,"  belonging  to  Karl  Winz,  a  mill  on  the  American  system 
was  erected  and  worked.  This  mill  contained  four  sets  of  stones  driven 
by  two  water-wheels. 


VIII 

FURTHER  DEVELOPMENT  OF  MILL-BUILDING  IN  EUROPE 

In  1823,  after  unsuccessful  attempts  by  Helfenberg  in  Rohrschach 
(Switzerland,  cant.  St.  Gallen),  Ballinger  in  Vienna,  and  von  Kollio  in 
Paris,  a  certain  von  Miiller  of  Lucerne  began  building,  first  in  Warsaw,  then 
in  Triest,  and  lastly  in  Frauenfeldt  in  Switzerland,  mills  which  operated 
by  means  of  iron  rolls  instead  of  millstones.  These  rolls  did  not  fulfil 
the  hopes  placed  in  them,  and  it  was  only  in  1834  that  a  Zurich  engineer, 
Sulzberger,  eliminated  the  defects  of  the  roller  mill  and  attained  real 
success.  The  joint  stock  company  established  by  Miiller  in  Frauen- 
feldt began  to  build  roller  mills  with  an  unusual  energy,  and  not  only 
successfully  erected  Muller's  mill  in  Warsaw,  Triest,  and  Frauenfeldt, 
but  took  pains  to  build  such  mills  in  other  localities  too.  These  mills 
were  driven  by  steam-engines.  With  a  steam-engine  and  a  sufficient 
quantity  of  fuel  and  water  for  feeding  the  boilers,  it  was  possible  to 
set  up  a  reliable  motor  anywhere. 

In  1836  there  were  several  steam-mills  in  Prussia  ;  Berlin  alone  was 
in  possession  of  three  of  the  number.  In  Austria-Hungary  the  first 
steam-mill  began  working  on  the  26th  September  1836  in  Odenburg  (in 
Hungary  in  the  neighbourhood  of  the  lake  Neusiedler).  About  that  time 
a  similar  mill  came  into  existence  in  the  Grand  Duchy  of  Baden  in  Mann- 
heim ;  a  little  later,  in  the  Grand  Duchy  of  Hessen,  two  large  steam-mills 
began  operating,  one  owned  by  Schneider  &  Co.  in  Oppenheim,  close 
to  the  banks  of  the  Rhine,  the  second  in  the  vicinity  of  Weissenau  by 
Mainz. 

In  Hanover  a  leaseholder,  Fiedler,  had  mill-plants  of  the  American 
type  in  Klickmuhle  (capital  of  Hanover)  in  1832,  and  the  first  steam-mill 
in  Rehden  was  started  by  Hartmann  in  1836. 

All  these  enterprises  enjoyed  great  success,  as,  thanks  to  them,  wheat 
gained  near  markets,  and  local  consumers  received  flour  of  a  higher 


CHAP.    l] 


FLOUR   MILLING 


35 


FIG.  29. 


36  FLOUR    MILLING  [CHAP,  i 

quality.  The  Hanover  steam-mill  in  Rehden,  which  ran  some  two  years 
only,  proved  to  be  the  sole  exception.  The  main  causes  of  its  failure 
were  the  restrictions  it  was  placed  under  by  the  restrictive  and  archaic 
regulations  imposed  by  the  trade  corporation  ;  besides  which  its  being 
situated  among  large  water-mills,  and  the  excessive  consumption  of  coal 
by  the  boilers,  were  factors  which  influenced  its  fate. 

The  first  wind-propelled  mill  of  the  American  type  in  Germany  is 
the  mill  by  Breslau,  constructed  by  Hofmann,  a  then  well-known  factory 
warrant  officer,  about  1836.  Fig.  29  shows  a  vertical  section  of  the  mill 
with  its  full  equipment. 

On  the  top  floor,  under  the  roof,  is  a  hollow  main  shaft  of  cast  iron  cc, 
with  spider  a  and  wings  &,  which  may  be  brought  into  any  position  (to 
assume  a  working  taper  of  the  surface  of  the  wings)  by  the  aid  of 
straight  and  angle  shafts,  moved  by  shaft  d  and  rope  e  with  a  shaft  k 
and  counterbalance  m.  The  motion  of  the  wind  propeller  is  transmitted 
by  means  of  cogged  wheels  e  and  /  to  the  vertical  main  shaft  A  of  the 
whole  plant. 

The  seventh  floor  (some  20  ft.  in  diameter)  contains  supply  bins  KK 
for  grain  and  an  appliance  for  elevating  it. 

The  sixth  floor  is  designed  for  grain- cleaning  apparatus,  of  which 
only  the  so-called  smutters  (machines  for  freeing  the  grain  of  its  husk) 
GG,  driven  by  gears  H  and  J,  are  shown  here.  From  this  floor  the  grain 
passes  into  bins  EE  on  the  fifth  floor.  In  all  probability,  other  cleaning 
machines  were  stationed  on  the  third  floor,  as  the  smutters  would  not 
be  sufficient  for  that  purpose. 

On  the  fourth  floor  we  find  the  stones  DD,  set  symmetrically  in  a 
circle,  the  radius  of  which  is  self-defined,  owing  to  a  large  cogged  wheel  B, 
which  couples  with  the  gears  of  the  spindles  of  all  four  millstones. 

On  the  third  floor  are  stationed  the  cogged  wheels  driving  the  mill- 
stones and  gears,  and  two  mill-drives  MM  for  collecting  the  grain  and 
cooling  the  product. 

We  may  add  that  of  the  four  pairs  of  millstones  (5  ft.  in  diameter), 
two  pairs  were  from  a  French  factory  (La  Ferte),  the  other  two  being 
from  the  Rhine  (of  volcanic  basalt  in  the  environs  of  Andernach).  These 
stones  made  from  100  to  110  revolutions  per  minute,  the  wind  pro- 
peller making  10  to  12  in  the  meantime. 

On  the  second  floor  are  the  sifting  bolters  NN.  The  middle  part  of 
that  section,  supported  by  strong  wooden  pillars,  serves  for  storage. 

In  the  ground  floor  is  the  hand-press  QR  for  packing  the  flour  pur- 
posed for  export  into  barrels  S. 


CHAP,  i]  FLOUR   MILLING  37 

IX 

THE  STRUGGLE  BETWEEN  THE  ROLLER  AND  STONE  MILLS 

The  first  steam  roller  mill  of  the  Sulzberger  (Frauenfeldt)  type 
appeared  at  the  end  of  1837  in  Mainz  ;  it  was  followed  by  similar  mills 
in  Stettin,  Munich,  and,  at  the  end  of  1837,  in  Leipzig. 

Steam  roller  mills  made  their  appearance  in  Austrian  dominions, 
Buda-Pest,  and  Milan,  probably  at  the  same  time. 

The  costs  of  arranging  such  a  mill,  with  a  capacity  up  to  300  centners  l 
of  wheat  per  day,  amounted  to  156,500  guldens,  with  a  floating  capital 
of  93,500  gulds. 

These  Sulzberger  roller  mills  were  adapted  solely  for  factory  pro- 
duction of  flour,  suitable  chiefly  for  export,  as  the  product  did  not 
become  heated  in  grinding,  while  it  was  possible  to  grind  only  perfectly 
dry  grain. 

The  roller-ground  flour  first  gained  great  popularity  from  its  good 
outward  appearance  and  high  quality.  It  was  even  maintained  that  this 
flour  contained  more  nutritive  matter  than  flour  ground  on  stones. 

In  Prechtl's  Technological  Encyclopedia  were  given  the  results  of  the 
analysis  of  flour  from  a  Milan  flour  mill  made  by  a  professor  of 
chemistry,  Ottavio  Ferrario. 

Roller-ground  flour  Stone-ground  flour 

Gluten          .         .         /       .         .  0-152  0'131 

Starch          ...         .         .  0'706  0'680 

Sugar  .        \.         .         .         .         .  0-052  0'048 

Gum   .-..         .         .         .  0-031  0-027 

Water  .         .         .         .         .  0-054  0'095 

Silicic  acid  .....  0*005  0*015 

Alum  .         . 0-003 

Lime    .  0-001 


1-000  I'OOO , 

But  gradually  the  opinion  as  regards  roller  mills  began  to  change,  to 
which  assistance  was  lent  by  the  circumstance  of  a  quick  discovery 
that  on  the  roller  mills  of  the  day  a  perfectly  pure  product  was  not  to 
be  obtained,  and  special  stone  sets  had  to  be  built  for  that  purpose. 

The  owners  of  roller  mills  soon  began  to  complain  of  heavy  expenses 
incurred  by  the  repair  and  oiling  of  the  rollers,  and  particularly  of  the 

1  Centner  =  hundredweight. 


38  FLOUR   MILLING  [CHAP,  i 

excessive  expenditure  of  power  and  the  necessity  of  employing  many 
hands.  Thus,  for  instance,  the  Ludwig  mill  in  Munich  produced 
13,000  Bavarian  bushels  of  flour  per  year  on  thirty-six  roller  mills, 
whereas  the  thirteen  stones  that  were  substituted  in  their  place  later, 
gave  26,000  bushels  of  flour,  while  the  number  of  hands  was  reduced 
from  twenty-eight  to  nine. 

In  Saxony  the  mills  of  the  Anglo-American  type  were  first  adopted 
at  the  end  of  1838  in  two  localities  :  in  Neumiihle  by  Dresden,  and  in 
Kloster-Miihle  in  Chemnitz.  Both  these  mills  were  worked  by  water- 
wheels  driving  millstone  sets. 

In  the  following  year  (1839),  in  Austria,  a  splendid  mill  was  started 
in  the  town  of  Fiume  (Croatia).  This  mill  was  situated  within  a  half- 
hour's  journey  from  the  sea.  It  contained  eighteen  sets  of  French  stones, 
4J  to  5 J  ft.  in  diameter,  driven  by  three  overshot  water-wheels  with  a  total 
capacity  of  95  h.p.  Its  capacity  was  to  be  198,000  centners  of  flour  from 
the  best  kinds  of  wheat — Banatka,  Russian,  and  Rumanian. 

In  1840  the  plan  of  construction  of  a  steam-driven  mill,  previously 
rejected,  was  worked  out  anew,  and  after  a  short  time  one  of  the  best 
Austrian  mills,  the  licensed  steam  mill  in  Vienna,  was  erected. 

The  renowned  firm  of  Coquerille,  in  Seraing,  near  Liege,  supplied  the 
mill  with  machinery,  arranged  it,  supervised  the  erection  of  it,  and  took 
the  whole  responsibility  upon  itself. 

In  1842,  when  the  mill  began  working,  it  was  equipped  with  sixteen 
sets  for  wheat  grinding,  and  two  for  that  of  corn.  In  course  of  time,  it 
was  enlarged  to  twenty-two  sets  driven  by  three  Wolf's  steam-engines, 
of  the  joint  capacity  of  200  h.p.  When  arranging  the  mill,  it  was 
designed  merely  for  the  Anglo-American  low  grinding  which  was  not 
adapted  for  producing  the  so-called  "  Imperial  Flour  "  (Kaiser  mehl), 
which  goes  to  the  baking  of  rolls,  very  popular  in  Vienna. 

Therefore  it  soon  had  to  be  reconstructed  for  semolina  grinding,  on 
the  French  system  or  "  Mouture  economique,"  to  be  discussed  later  in  the 
section  treating  of  grists. 

In  this  manner  the  stone  mill  won  the  battle  almost  everywhere. 
Between  the  forties  and  to  the  sixties,  the  roller  mill  struggled  in  vain 
against  the  millstone  set,  improved  by  a  system  of  exhausts  and  dust 
collection. 

However,  at  the  end  of  the  sixties,  the  factories  of  Escher,  Wyss  &  Co.. 
near  Vienna,  and  F.  Wegmann  in  Zurich,  brought  out  the  perfected  roller 
mills,  which  began  successfully  to  supplant  the  stone  set  in  the  indus- 
trial flour  mills. 


CHAPTER    II 

GENERAL    IDEAS    OF   THE    RAW   MATERIALS   FOR 
FLOUR   PRODUCTION 


THE  BERRIES  OF  THE  CEREALS 

THE  berries  of  the  cereals  are  the  pre-eminent  raw  materials  of  the  milling 
industry.  In  order  to  understand  the  working  of  the  various  grain-clean- 
ing and  grain-grinding  machines  and  to  study  the  nutritive  qualities  of  the 
products  of  the  grain,  it  is  necessary  to  be  acquainted  with  the  structure 
and  the  chemical  composition  of  the  berries  of  the  different  cereals. 

On  first  examination  we  see  that  the  berry  of  the  cereals  has  an  oval 
form.  If  viewed  through  a  magnifying  glass  some  hairs,  either  forming 
a  sort  of  beard  (wheat,  rye)  or  covering  the  whole  body  of  the  grain 
(oats),  are  perceived  at  one  end  of  it,  and  the  germ  or  the  embryo  at  the 
other.  On  examining  a  slightly  magnified  section  through  the  berry 
we  can  see  that  it  consists  of  a  starchy  nucleus,  surrounded  by  several 
coats  or  skins ;  if  we  magnify  the  section  150  times  we  can  discern  six 
such  coats  which  may  be  detached  more  or  less  easily  from  the  berry. 
Flour  or  groats  are  made  of  the  nucleus,  and  the  skins  yield  bran,  a  by- 
product of  flour  manufacture. 

Each  of  the  skins  consists  of  several  separate  layers  that  cannot  be 
easily  detached  one  from  another.  We  shall  investigate  them  more  closely 
when  examining  the  wheat  berry,  and  will  now  proceed  to  consider  them 
briefly. 

The  first  three  skins  of  the  cereal  berry  (see  Fig.  30)  are  called  outer 
envelopes  or  envelopes  of  the  fruit,  the  two  second  are  the  envelopes  of 
the  seed  proper,  the  last  one  is  (inaccurately)  called  the  gluten  envelope. 

The  first  envelope  A  (Epidermis,  Epicarpium)  consists  of  thick-walled 
cells  filled  with  air,  and  disposed  along  the  longitudinal  axis  of  the  berry. 
Its  outer  surface  is  either  smooth  or  shrivelled,  its  colour  varies  according 
to  the  species  of  the  cereal.  It  is  often  pierced  through  by  hairs,  acting 
as  air-conducting  channels  while  the  grain  is  ripening. 

The    second    envelope    B    (Mesocarpium,    Sarocarpium)    consists    of 

39 


40 


FLOUR   MILLING 


[CHAP,  it 


colourless,  or  sometimes  yellowish,  loosely  built  cells.     It  is  very  thin 
and  possesses  no  well-outlined  characteristics. 

The  third  envelope  C  (Endocarpium)  is  composed  of  cells  disposed  at 

right  angles  to  the  axis  of  the  berry.     While  this  latter  is  still  unripe 

the  envelope  is  of  a  greenish  colour,  when  quite  ripe  it  becomes  colourless. 

These  three  envelopes  may  be  comparatively  easily  taken  off  the  seed. 

The  fourth  envelope  D   (Testa  Episperm)   has   oblong   cells,   much 

smaller  in  size  than  those  of  the  outer 
envelopes. 

The  fourth  envelope  D  and  the 
fifth  E  (Embryonic  membrane)  are 
called  envelopes  of  the  berry  proper. 
They  are  both  very  thin,  adjoin  closely 
to  each  other,  and  it  is  most  difficult 
to  detach  them  one  from  another. 

The  sixth  envelope  F  (Perisperm) 
is  a  layer  of  aleurone,  and  is  also 
called     the    gluten    envelope.       Its 
volume  constitutes  one  third  of  the 
total  volume  of  all  the  envelopes.    Its 
cells  have   very   stout   walls  ;   they 
are  very  hygroscopic,  and  being  put 
in  water  soon  become  swollen.     It 
was  formerly  supposed  that  they  con- 
tained gluten  (anendosperm-nitrogen^ 
ous  substance),  and  the  envelope  was 
therefore  called  the  gluten  envelope. 
And  though  the  careful  analyses  made 
by  Shenk  and  Brucke   have  shown 
that  these  cells  do  not  contain  any  gluten  at  all,  the  term  is  still  in  use. 
The  gluten  envelope  comes  into  a  close  touch  with  the  endosperm 
and  the  envelopes  of  the  seed  proper.     It  is  therefore  possible  to  take  off 
the  three  inner  envelopes  of  the  berry  without  breaking  this  latter. 

The  nucleus  G  (Endosperm)  that  yields  flour  when  broken,  consists 
of  comparatively  small  cells  with  thin,  colourless  walls.  The  cells  of  the 
endosperm  are  filled  with  granules  of  starch  and  very  small  granules  of 
gluten  (cleber).  The  nearer  to  the  centre  of  nucleus  the  smaller  is  the 
proportion  of  gluten  in  the  cells.  The  largest  quantity  of  it  is  contained 
by  the  cells  that  adjoin  the  sixth  envelope  of  the  berry. 

A  section  through  the  nucleus  is  either  flour- white,  or  has  the  appear- 


FIG.  30. 


CHAP,  n]  FLOUH   MILLING  41 

ance  of  a  glassy,  somewhat  yellowish  substance.  The  colour  of  the 
nucleus  darkens  gradually  from  the  centre  towards  the  outer  cells. 

The  germ  H  of  the  berry  is  firmly  attached  to  the  nucleus.  Its  cells 
are  tiny  and  very  compact,  and  contain  much  nitrogen,  mineral  salts, 
and  fats.  While  the  plant  is  developing  the  germ  is  fed  on  the  starch 
and  the  cleber  of  the  nucleus.  This  accounts  for  the  so-called  germina- 
tion of  the  raw  grain  kept  in  a  warm  place. 

The  envelopes  are  not,  as  we  are  going  to  see,  of  a  nutritive  nature, 
and  must  therefore  be  removed  before  the  endosperm  is  finally  reduced  to 
flour.  Their  total  weight  constitutes  from  17*6  per  cent,  to  30  per  cent,  of 
the  weight  of  the  berry. 

Let  us  now  examine  in  detail  the  wheat  berry. 


II 

PHYSICAL  STRUCTURE  OF  THE  WHEAT  GRAIN 

The  functions  of  the  grain  are  those  of  reproduction,  hence  its  struc- 
ture. The  grain  consists  of  three  distinct  parts :  the  germ,  the  endosperm, 
and  the  bran.  The  germ  is  the  seed  properly  speaking,  for  it  develops 
ultimately  into  the  plant.  The  endosperm  consists  of  a  starchy  sub- 
stance ;  it  constitutes  the  main  body  of  the  grain,  and  is  destined  to  supply 
food  to  the  germ  in  the  early  period  of  its  growth.  The  bran  consists 
of  several  separate  coverings,  which  enclose  both  germ  and  endosperm, 
and  are  destined  to  protect  the  grain. 

The  study  of  the  physical  structure  of  the  grain  requires  the  use  of 
the  microscope. 

Fig.  31  represents  a  section  through  the  crease  of  the  grain,  shown  in 
elevation  by  shading  on  the  left-hand  side  of  the  sketch.  The  figure  has 
been  obtained  by  tracing  from  typical  slides,  and  reproduces  fairly  well 
the  relative  dimensions  of  the  germ  and  the  endosperm.  The  bran  is 
seen  to  enclose  both.  With  the  aid  of  a  microscope  one  can  see  the 
so-called  aleurone  cells  or  the  square  cells  of  the  bran  lining  the  interior. 
The  name  "gluten"  cells,  though  commonly  used,  is  not  accurate,  for 
these  cells  contain  no  gluten. 

Fig.  32  shows  a  cross  section  through  the  germ  of  a  Kubanka  wheat 
grain.  Here  we  see  the  pigment-containing  cells  going  all  round  the 
grain  and  forming  in  the  crease  a  thick  spot  of  colour.  The  aleurone 
cells  of  the  bran  do  not  continue  round  the  germ.  The  next  figure  (33) 
represents  the  same  section,  but  examined  with  a  higher  power  objective. 


42 


FLOUR   MILLING 


[CHAP,  it 


Hairs  of  Heard. 


Cuticle. 
Epicarp. 
Endocarp. 
Episperm. 
Aleut-one  Cells. 


-BRAN. 


It  shows  more  clearly  the  outer  skins  of  the  bran  and  allows  us  to  see 
quite  distinctly  the  square  aleurone  or  cerealin  cells.  At  the  bottom  of 
the  crease  they  become  more  numerous  and  form  a  double  line.  The 
bifurcation  of  the  crease  is  perfectly  distinct.  The  rather  large  dark 
yellow  spot  of  pigment  cells  is  plainly  seen  in  the  middle  of  the  fork. 
The  starch  granules  are  also  seen. 

In  order  to  examine  the  bran  and  the  endosperm  we  must  select  a  very 

thin  section.  The  bran  consists 
of  the  outer  envelopes  of  the 
grain  and  those  of  the  seed 
proper.  Fig.  34  shows  them  all 
on  a  longitudinal  section. 

a  is  the  outer  "  epidermis  " 
or  cuticle.  It  constitutes,  ac- 
cording to  Mege  Mouries,  0'5 
per  cent,  by  weight  of  the  whole 
grain,  and  consists  of  thick- 
walled,  longitudinally  disposed 
cells.  It  is  often  pierced  through 
by  hairs  acting  as  air-conduct- 
ing channels  while  the  grain  is 
ripening. 

6  is  the  "epicarp."  This 
amounts  to  about  1  per  cent, 
of  the  grain ;  it  is  very  thin 
and  possesses  no  well-defined 
characteristics. 

c  is  the  "  endocarp  "  and 
the  last  of  the  outer  series  of 
the  grain  envelopes.  Its  cells 


t  Starch  eett  fitted 
(with  granules, 
f  Parenchymatous 
I  cellulose  dividing 
\  endosperm  into 
\8tarch  cells. 


(Compressed  empty 
\cellsofeiidosperm. 
(  Termination  of 
\  aleurone  cells  at 
*-  commencement  of  Germ. 
)  Absorptive  &  secre- 
\tive  epithelium. 
Plumula  sheath. 
Scutellum. 
f Elongated  cells  of 
..    I  scutellum. 
I  Rudimentary  leaves 
)  of  Plumula. 
f  Testa  or  continuous 
J  envelope  enclosing 
|  both  Endosperm 
\and  Germ. 


Radicle. 
Root  Sheath. 
Radicle  Cap. 

E.  Endosperm. 
G.  Germ. 


FIG.  31. — Longitudinal  Section  through  a  Grain  of 
Wheat,  magnified  about  10  Diameters. 


are  disposed  at  right  angles  to  the  axis  of  the  grain,  and  appear  to  be 
almost  round  on  the  longitudinal  section.  Its  weight  constitutes  1*5  per 
cent,  of  that  of  the  grain. 

d  is  the  "  testa,"  the  first  of  the  two  envelopes  of  the  seed  proper.  It 
is  also  called  "episperm."  It  consists  of  oblong  cells  much  smaller  in 
size  than  those  of  the  outer  envelopes  and  contains  most  of  the  colouring 
matter  of  the  grain. 

e  is  the  "  embryonic  membrane  "  and  the  second  envelope  of  the  seed 
proper.  It  is  very  thin  and  closely  adjoins  the  testa.  Together  they 
constitute  2  per  cent,  of  the  grain. 


CHAP.    II] 


FLOUR    MILLING 


/  is  the  layer  of  "  aleurone  "  cells.  These  cells  appear  to  be  almost 
square  in  outline  and  have  very  stout  walls.  They  absorb  moisture 
easily,  and  being  put  in  water,  soon  become  swollen.  As  already  men- 
tioned, they  only  enclose  the  endosperm  and  do  not  envelop  the  germ. 


FIG.  32. — Transverse  Section  of  Grain  of 
Wheat,  magnified  13  Diameters. 


FIG.  33. — View  of  Crease  in  Grain  of  Wheat, 
as  shown  in  a  Transverse  Section. 


g  is  the  layer  of  parenchymatous  cellulose,  which  divides  the  endo- 
sperm into  comparatively  large  cells.  These  latter  are  filled  with 
granules  of  starch  and  very  small  granules  of  gluten.  Towards  the 
centre  of  the  endosperm  the  proportion  of  gluten  becomes  smaller. 


FIG.  34. — Longitudinal  Section  through 
Bran  and  Portion  of  Endosperm  of 
Grain  of  Wheat,  magnified  440  Diameters. 


FIG.  35. — Outer  Layer  of  the  Bran  of 
Wheat,  magnified  250  Diameters. 


h  is  the  "  hilum  "  of  an  individual  starch  granule. 
The  envelopes  must  be  also  examined  on  the  flat.     They  can  be 
detached  easily  enough  off  the  body  of  the  grain  in  three  layers,  (1)  epi- 


44 


FLOUR   MILLING 


[CHAP,  it 


dermis  and  epicarp,  (2)  endocarp  and  episperm,  and  (3)  the  inner  skin 
which  contains  the  cerealin  cells.  Fig.  35  shows  the  structure  of  the 
outer  layer.  Its  cells  are  arranged  longitudinally  in  the  direction  of 
the  grain  and  are  four  to  six  times  larger  in  length  than  in  breadth. 
Fig.  36  represents  the  hairs  of  the  beard  at  the  end  of  the  grain.  We 
can  see  on  the  section  itself  how  they  are  attached  to  the  skin  ;  the 

mount  also  shows  canals  ex- 
tending about  half  the  length 
of  the  hair.  Fig.  37  shows  the 
structure  of  the  second  layer. 
We  see  that  it  consists  of  two 
layers,  one  over  the  other,  which 

FIG.  36. — Beard  of  Grain  of  Wheat.  .     J .  ,. 

are   not   both   in   focus  at  the 

same  time.  The  upper  layer  consists  of  a  series  of  long  cells  often 
termed  "  girdle  "  cells,  and  arranged  transversely  to  the  longitudinal 
section  of  the  grain,  as  shown  on  Fig.  34  (marked  c).  On  this  they  seem 
to  be  almost  round.  Underneath  the  girdle  cells  are  the  pigment- 
containing  cells. 

Fig.  38  shows  the  aleurone  or  cerealin  cells  of  the  bran  to  be  of  an 


FIG.  37.— Middle  Layer  of  the  Bran  of 
Wheat,  magnified  250  Diameters. 


FIG.  38. — Inner  or  Aleurone  Layer  of  the 
Bran  of  Wheat,  magnified  440  Diameters. 


irregular  outline,  though  when  viewed  on  section,  either  longitudinal  or 
transverse,  they  appear  to  be  square  or  rectangular,  and  are  therefore 
often  termed  cubical. 

Let  us  now  compare  the  longitudinal  section  through  the  bran  of 
wheat,  as  shown  on  Fig.  34,  with  its  transversal  section  shown  on  Fig.  39. 


CHAP.    II] 


FLOUR    MILLING 


45 


Though  the  latter  section  was  not  so  good  as  the  longitudinal,  the 
drawing  shows  clearly  enough  the  general  structure  of  the  bran.  The 
cells  of  the  middle  skin  appear  to  be  of  considerable  length  when  we 
see  them  on  the  flat.  When  we  look  on  them  lengthwise,  we  must,  of 
course,  notice  the  ends  of  the  cells  of  the  outer  skin.  The  aleurone 
cells  appear  more  irregular  in  outline  on  the  transversal  section  than  on 
the  longitudinal.  The  study  of 
these  drawings  must,  of  course, 
be  followed  by  an  examination 
of  the  actual  slides  under  the 
microscope. 

The  bran  of  the  wheat  berry 
is  chiefly  composed  of  cellulose 


FIG.  39. — Transverse  Section  through  Bran  of 
Wheat,  magnified  250  Diameters. 


or  woody  fibre  and  of  solu- 
ble albuminous  matter.  When 
treated  with  hot  dilute  solutions  of  acid  and  alkali  it  yields  cellulose  in  a 
fairly  pure  state.  The  following  is  the  way  to  obtain  cellulose  for  the 
purpose  of  microscopic  study  :  pieces  of  the  different  layers  of  bran  are 
put  in  separate  test-tubes  and  subjected  for  an  hour  to  the  action  of  dilute 


FIG.  40.— Cellulose  of  Outer  Skin  of 
Bran,  magnified  250  Diameters. 


FIG.  41.— Cellulose  of  Middle  Skin  of 
Bran,  magnified  250  Diameters. 


sulphuric  acid.  Then  this  latter  is  poured  off  and  substituted  by  caustic 
soda  solution,  in  which  the  pieces  of  bran  are  digested  for  another  hour. 
Then  solutions  of  1  part  respectively  of  acid  and  alkali  and  20  parts  of 
water  are  used,  and  the  resulting  cellulose  can  be  mounted  on  glass 
glides, 


46 


FLOUR    MILLING 


[CHAP,  ii 


Figs.  40,  41,  42,  and  43  show  respectively  the  cellulose  of  the  outer, 
middle,  and  aleurone  layers  of  bran  as  viewed  under  the  microscope. 
The  structure  of  the  first  and  second  pieces  of  cellulose  does  not  differ 
much  from  the  structure  of  the  original  layer  of  skin.  The  first  appears 
to  be  almost  transparent,  and  in  the  second  the  underlying  pigment 
cells  are  partly  stripped  off.  The  aleurone  layer  changes  considerably 
in  appearance,  when  treated  with  alkali,  for  it  contains  a  large  quantity 
of  protein  matter.  Fig.  42  shows  a  piece  of  this  layer,  in  which  the 
greatest  part  of  protein  has  been  removed  by  the  action  of  the  caustic 
soda.  Fig.  43  shows  another  specimen,  in  which  there  remains  almost 
no  protein  at  all. 

The  outer  layer  of  wheat  bran  is  thus  largely  composed  of  cellulose, 


FIG.  42. — Cellulose  of  Aleurone  Layer  of 
Bran,  with  Portion  of  Protein  re- 
maining, magnified  440  Diameters. 


FIG.  43. — Cellulose  of  Aleurone  Layer 
of  Bran,  with  only  the  slightest  Trace 
of  Protein  still  remaining  in  some  of 
the  Cells,  magnified  440  Diameters. 


and  cannot,  therefore,  be  used  for  human  food.  The  middle  layer 
contains  less  cellulose,  but  a  larger  quantity  of  colouring  matter. 
The  inner  contains  but  a  very  small  proportion  of  cellulose  and 
large  quantities  of  protein.  This  latter  is  injurious  to  the  flour, 
for  it  exerts  a  strong  action  on  broken  starch  granules.  None 
of  the  three  must  be  therefore  admitted  as  a  part  component  of 
the  flour. 

If  separated  from  the  bran  and  subjected  to  acid  and  alkali  treat- 
ment, the  endosperm  yields  traces  of  cellulose.  It  is  most  instructive 
to  subject  to  the  same  treatment  several  different  varieties  of  flour. 


CHAP.    II] 


FLOUR   MILLING 


47 


This  will  allow  the  student  to  examine  (1)  whether  the  flour  contains  a 
large  proportion  of  particles  of  bran,  and  (2)  whether  the  latter  remains 
intact,  or  portions  of  it  have  been  detached  from  one  of  the  surfaces 
and  ground  into  flour. 


III 

CHEMICAL  COMPOSITION  OF  WHEAT 

The  grains  of  the  cereals  consist,  as  shown  by  analysis,  chiefly  of  the 
following  substances  :  fat,  starch,  cellulose,  dextrin,  sucrose,  probably 
also  other  kinds  of  sugar  ;  soluble  protein  bodies  ;  albumin,  globulin, 
and  proteose  ;  insoluble  protein  bodies  ;  glutenin  and  gliadin,  which 
together  constitute  gluten ;  mineral  matters,  principally  potassium 
phosphate,  and  finally  water. 

Bell  has  tabulated  as  follows  the  average  composition  of  the  different 
cereals : 


TABLE   I 


Wheat. 

Carolina 

CONSTITUENTS. 

Long- 
eared 

English 
Oats. 

Maize. 

Rye. 

Rice 
without 

Winter. 

Spring. 

Barley. 

Husk. 

Fat 

148 

1-56 

1-03 

5-14 

3-58 

1-43 

0-19 

Starch    .         . 

63-71 

65-86 

63-51 

49-78 

64-66 

61-87 

77-66 

Cellulose 

3-03 

2-93 

7-28 

15-53 

1-86 

3-23 

Traces. 

Sugar  (as  cane) 

2-57 

.  2-24 

1-34 

2-36 

1-94 

4-30 

0-38 

Albumin,  &c.,  insol-| 
uble  in  alcohol     .  / 

10-70 

7-19 

8-18 

10-62 

9-67 

9-78 

7-94 

Other      nitrogenousl 

matter  soluble  in  I 

4-83 

4-40 

3-28 

4-05 

4-60 

5-09 

1-40 

alcohol         .         .  J 

Mineral  matter 

1-60 

1-74 

2-32 

2-66 

1-35 

1-85 

0-28 

Moisture 

12-08 

14-08 

13-06 

11-86 

12-34 

12-45 

12-15 

Total 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

Another  comparative  table  of  the  composition  of  cereals  was  drawn 
ip  later  by  Clifford  Richardson.  In  this  the  moisture  figures  are  con- 
siderably lower  than  in  Bell's  analyses,  a  fact  that  is  due  probably 

the  greater  dryness  of  the  American  climate. 


48 


FLOUR    MILLING 


[CHAP,  ij 


TABLE   II 

AVERAGES  or  DETAILED  ANALYSES  OF  CEREALS 


NUMBER  OP  ANALYSES. 

Wheat 

27 

Barley 
14 

Oats 
18     . 

Maize 
21 

Rye 

17 

Fat          

2-30 

2-67 

7-87 

5-54 

1-83 

Starch    . 

67-88 

62-09 

56-91 

66-91 

61-87 

Cellulose 

1-90 

3-81 

1-29 

1-41 

1-47 

Sugar,  &c.       ..... 

3-50 

7-02 

6-07 

2-18 

7-57 

Dextrin  and  soluble  starch 

2-30 

3-55 

3-47 

2-18 

4-75 

Proteins  insolublein  80  per  cent.  alcohol 

7-45 

7-86 

13-43 

4-96 

9-07 

Proteins  soluble  in  80  per  cent,  alcohol 

3-58 

3-66 

1-82 

5-84 

2-53 

Mineral  matter         .... 

1-84 

2-87 

2-22 

1-54 

2-06 

Moisture         

9-25 

6-47 

6-92 

9-34 

8-85 

Total       

100-00 

100-00 

100-00 

100-00 

100-00 

Ratio  of  proteins  to  carbohydrates    . 

6-9 

6-5 

4-8 

7-6 

6-5 

Still  later  Hutchinson  represented  the  general  composition  of  the 
cereals  in  the  following  table  : 

TABLE   III 


CONSTITUENTS. 

Wheat. 

Barley. 

Oats, 
Rolled. 

Maize. 

Rye. 

Rice,  no 
Husk. 

Millet. 

Buck- 
wheat. 

Fat    . 

1-7 

1-9 

8-1 

5-4 

2-3 

2-0 

3-9 

2-2 

Carbohydrates  . 

71-2 

69-5 

68-6 

68-9 

72-3 

76-8 

68-3 

61-3 

Cellulose  . 

2-2 

3-8 

1-3 

2-0 

2-1 

1-0 

2-9 

11-1 

Proteins  . 

11-0 

10-1 

13-0 

9-7 

10-2 

7-2 

10-4 

10-2 

Mineral  matter 

1-9 

24 

2-1 

1-5 

2-1 

1-0 

2-2 

2-2 

Water      . 

12-0 

12-3 

6-9 

12-5 

11-0 

12-0 

12-3 

13-0 

Analyses  of  Wheats  from  Different  Countries. — The  tables  on  pp.  50-54 
are  the  results  of  a  series  of  analyses  made  by  W.  Jago.  The  first  eighteen 
were  made  in  1884  on  specimens  of  English  wheat  of  the  1883  and  1884 
harvests,  and  still  represent  fairly  well  the  general  composition  and 
character  of  English  wheats. 

Nos.  1-18  are  samples  of  1883  wheats,  except  where  otherwise  men- 
tioned. The  figures  of  moisture,  of  soluble  extracts  and  proteins  are 
rather  high,  while  those  of  gluten  are  lower  than  in  foreign  wheats. 
The  Revitts  yielded  exceedingly  small  traces  of  gluten,  so  small  that  it 
was  practically  impossible  to  recover  them  from  the  bran, 


CHAP,  n]  FLOUR    MILLING  40 

Nos.  19-27  are  all  1883  samples  of  wheats  used  by  the  millers  of  the 
south  of  England.  Nos.  19  and  20  are  samples  of  the  same  variety,  but 
grown  in  different  localities.  No.  21  is  a  sample  damaged  during  growth. 
Nos.  28-38  are  fine  quality  samples  of  the  south  and  western  counties, 
all  of  the  harvest  of  1884. 

If  compared  to  those  of  1883  the  figures  of  moisture,  soluble  extract, 
and  soluble  proteins  are  rather  low.  The  average  of  the  glutens 
is  also  lower.  In  the  1883  series  No.  18,  a  Scotch  west-country 
specimen,  yielded  the  lowest  percentage  of  gluten,  5*00,  and  the  highest 
of  moisture,  16- 18.  Similarly,  No.  38  of  the  1884  series,  grown  in  a 
damp  climate,  South  Devon,  yields  5'00  per  cent,  of  gluten  and  16*20 
per  cent,  of  moisture. 

Since  1884  several  new  varieties  of  wheat  have  been  introduced  in 
England.  Among  these,  two  varieties,  "  Tiverson's "  and  "  Webb's 
Stand-up,"  are  largely  cultivated  now.  French  wheats  and  the  Hard 
Fife  are  also  grown  to  some  extent. 

The  foreign  wheats  present,  of  course,  a  greater  number  of  varieties 
than  the  English.  A  comparison  between  the  moistures  and  the  glutens 
of  wheats  and  the  flours  produced  from  them  is  most  instructive. 
Russian  wheats  yield  generally  a  higher  percentage  of  gluten  than  the 
American.  The  Indian  are,  as  a  rule,  rather  poor,  both  in  gluten  and  in 
moisture.  They  appear  to  be  almost  sandy.  When  worked  up  with 
water,  and  only  after  long  "  conditioning,"  they  acquire  the  charac- 
teristic ductility  of  wheaten  flours.  The  Persian  wheats  contain  more 
gluten  than  the  Indian,  especially  the  clean  Persian,  No.  68. 

No.  78  comes  from  Winona,  U.S.A.,  and  serves  to  make  flours  Nos.  8 
and  9.  The  upper  set  of  gluten  estimations  was  obtained  after  the 
dough  had  stood  for  two  hours.  The  wheat  itself  and  the  flours  pro- 
duced from  it  absorb  water  extremely  slowly.  No.  80  comes  from 
Manitoba.  The  comparatively  high  percentage  of  moisture,  soluble 
extract,  and  proteins  are  characteristic  of  the  cold  climate. 

The  sources  of  British  supply  have  greatly  changed  since  the  time 
when  these  analyses  were  made.  London  gets  now  almost  none  of  the 
United  States  spring  wheats.  The  Duluth  wheats  have  been  largely 
substituted  by  the  Manitoba.  Durum  wheat  is  imported  from  the 
United  States  in  considerable  quantities.  *  The  winter  Americans  are 
known  as  Red  Winter  and  Hard  Winter.  The  Russian  wheats  known  as 
Saxonka  and  Kubanka  have  also  almost  disappeared  from  the  London 
market,  being  substituted  by  several  other  varieties  (Ghirka,  Asima,  and 
others). 


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CHAP.   Il] 


FLOUR    MILLING 


55 


Composition  and  Weight  of  Wheats  according  to  Professor  Fleurent.- 
Professor  Fleurent  has  analysed  certain  hard  wheats,  Russian,  Algerian, 
and  Canadian  (the  last  contained  25  to  30  per  cent,  of  soft  wheat),  and 
tabulated  the  results  as  follows  : 


TABLE   VII 


Russian  Wheat. 

Algerian  Wheat. 

Canadian  (loose 
Wheat. 

Average  weight  of  grain  in  grams     . 

0-030 

0-048 

0-037 

Constitution,  per  cent.  : 

Endosperm         .         . 

84-95 

84-99 

84-94 

Embryo     .          .          .          . 

2-00 

1-50 

2-05 

Husk                         ,:  .;.         .         . 

13-05 

13-51 

13-01 

Composition  of  the  Entire  Wheat. 

Water  .       -.         .'^    |> 

.  1142 

11-34 

11-36 

Nitrogenous  matter  : 

Gluten     ...         .         ..." 

14-76 

11-00 

10-88 

Soluble  (diastases,  &c.)       .       ".. 

2-25 

1-82 

1-67 

Ligneous,  of  husk 

1-82 

1-90 

1-91 

Starch           .         . 

50-15 

55-05 

54-55 

Fatty  matters        .        .  .         . 

1-18 

1-93 

2-70 

Soluble  carbohydrates  : 

Sugars     .         .      ;   . 

2-17 

2-68 

2-18 

Galastose 

0-65 

0-46 

0-75 

Of  husk  .  .      .         . 

1-76 

2-19 

1-90 

Cellulose      "  .       ,  v 

9-73 

9-40 

£-21 

Mineral  matters     .         .         .         .'•- 

1-56 

1-42 

1-35 

Undetermined  and  loss  . 

2-48 

0-81 

1-54 

Total    .         . 

100-00 

100-00 

100-00 

The  gluten  contained  by  the  Russian  wheat  consisted  of  gliadin, 
46' 45  per  cent.,  glutenin  37 '89  per  cent.,  and  congluten  15-66  per  cent. 
Fleurent  considers  the  congluten  to  be  the  cause  of  the  want  of  elasticity 
of  the  flour  obtained  from  hard  wheats. 

Composition  and  Properties  of  Durum  Wheat  and  Flour. — Durum 
wheat,  Tricitum  durum,  is  cultivated  in  considerable  quantities  near  the 
Mediterranean  and  in  Southern  Russia,  and  is  chiefly  grown  for  the  manu- 
facture of  macaroni.  It  has  been  also  introduced  recently  in  America, 
where  bread  flours  are  manufactured  from  it.  Its  grains  are  hard,  am- 
bertiated,  and  almost  twice  as  large  as  those  of  ordinary  Russian  wheats 
Norton,  of  the  South  Dakota  Agricultural  Experiment  Station,  has 


56 


FLOUR    MILLING 


[CHAP,  ii 


analysed  durum  wheat  and  investigated  its  properties.  Also  comparative 
analyses  of  Kubanka,  one  of  the  best  Russian  durum  wheats,  and  Min- 
nesota, one  of  the  best  American  bread  wheats,  have  been  carried  out  and 
tabulated  together  with  the  mean  of  American  wheats  (by  the  Bureau 
of  Chemistry  of  the  Department  of  Agriculture,  U.S.A.). 


TABLE    VIII 


CONSTITUENTS. 

Kubanka  Durum 
Wheat. 

Minnesota  Bread 
Wheat. 

Mean  of  American 
Wheat. 

Water     r  .         '.         .         .       $i 

3-32 

6-00 

10-62 

Mineral  matter  . 

1-71 

2-46 

1-82 

Fat   .          .•'-,-       .    '      «    '  ,:-•.  , 

2-34 

2-49 

1-77 

Crude  fibre          .          .          . 

2-52 

3-35 

2-36 

Crude  protein  N  x  5-7         -...'• 

14-46 

13-21 

12-23 

Carbohydrates  other  than  crude  fibre 

69-65 

72-49 

71-18 

Sugar        V        .       ..  v- 

3-26 

1-42 

.  . 

Dextrin     .         .         .         » 

1-25 

.  . 

Invert  sugar,  soluble  starch 

Nil 

Nil 

The  percentage  of  sugar  and  of  dextrin  is  remarkably  high.  Accord- 
ing to  Stone,  ordinary  wheats  contain  0'27  to  0*41  per  cent,  of  dextrin. 
The  flour  obtained  from  durum  wheat  is  estimated  to  contain  1  to  2  per 
cent,  of  sucrose,  while  the  ordinary  samples  analysed  by  Stone  only  gave 
0'18  to  0-20  per  cent. 

The  American  durum  wheat  contains  more  protein  than  that  origin- 
ally imported.  Calculations  on  a  water-free  basis  have  given  the 
following  results  : 

TABLE   IX 


Number  of 
Analyses. 

Protein 
NX  57. 

Imported  seed      ..  .  ••'•„'• 

7 

15-73  per  cent. 

Crop  of  1901   .         . 

31 

18-13        „ 

„       1902  . 

32 

14-57        „ 

„       1903   .         ,         :.:        . 

45 

17-34 

The  harvest  of  1902  was  rather  bad. 

The  durum  flour  has  a  deep  yellow  tint,  that  shows  0*25  yellow -f  0*17 
orange  on  the  Lovibond  tintometer  scale.  The  colouring  substance  is 
insoluble  in  distilled  water,  but  can  be  dissolved  in  ether,  alcohol,  and 


CHAP,  ii]  FLOUR    MILLING  57 

dilute  alkalies.  From  the  later  solutions  it  may  be  discharged  by  acids. 
This  accounts  probably  for  the  fact  that  flour  is  stained  yellow  by  the 
addition  of  sodium  carbonate. 

A  series  of  determinations  made  on  durum  flours  gave  the  following 
figures  (the  gliadins  were  calculated  on  a  water-free  basis) : 

Crude  protein    .          .  ,  :' „•'  .  W  15-00  per  cent. 

Wet  gluten        .         .  .  '  .  ..  -•;  53-77 

Dry  gluten         *         ~  '  .  .  .  .  17-68 

Gliadin     .          .          .  .  .  .:  '-.  7-87 

Gliadin  of  total  protein  .  .  .  .  47-17          „ 

The  percentage  of  gluten  runs  very  high,  as  well  as  that  of  sugar.  And 
yet  the  flour  possesses  but  little  elasticity  and  very  poor  adhesive  qualities, 
properties  that  are  usually  ascribed  to  lack  of  gliadin.  Bread  made 
with  the  poorer  durum  flours  rises  neither  during  the  fermentation,  nor 
in  the  oven. 

The  baker's  sponging  test  shows  that  good  durum  flours  have  as  high 
a  volume  as  the  bread  wheat  flours.  But  durum  flour  becomes  more 
sticky  than  these  latter  ;  when  the  doughs  are  somewhat  stiff  they  do 
not  rise  properly,  and  the  bread  obtained  is  heavy  and  poor  of  texture. 
Yet,  when  water  is  used  in  sufficient  quantity,  the  volume,  weight,  and 
texture  of  durum  breads  are  not  below  those  prepared  with  ordinary 
wheat  flours. 


CHAPTER   III 

PREPARATION    OF   GRAIN   FOR    GRINDING 

I 

IMPURITIES  AND  THE  PRINCIPLES  OF  CLEANING 

As  we  have  already  seen  in  the  general  review  of  the  grain,  the 
impurity  of  the  stock  is  due  to  the  character  of  the  production.  An 
admixture  of  seed  of  other  plants  is  unavoidable  even  when  the  culture 
of  the  cereals  is  most  careful.  The  separation  of  the  seeds  of  foreign 
plants  from  the  grain,  although  performed  on  the  larger  farms,  is  not 
satisfactory,  the  grain  being  usually  prepared  for  sowing  and  not  for  sale. 
The  grain  of  the  large  rationally  worked  farms  is  comparatively  clean ; 
that  of  the  Russian  peasantry  and  small  farms,  on  the  other  hand,  some- 
times contains  up  to  6  per  cent,  of  impurities. 

In  addition  to  the  seeds  of  foreign  plants,  the  grains  of  bad  quality  of 
the  corn  itself  belong  to  the  impurities.  Those  are  mainly  the  so-called 
"  shrivelled  "  kernels,  unripe  at  the  time  of  harvesting  and  dried  to  light 
meagre  grains,  or  those  appertaining  to  harvests  caught  by  drought  and 
admixed  to  the  normal  grain.  Kernels  of  corn  stricken  by  some  disease, 
e.g.  smut,  are  also  of  this  group. 

Assuming  the  corn  to  be  ground  at  the  mill  is  wheat,  the  kernels  of 
other  cereals,  such  as  rye,  barley,  oats,  &c.,  are  to  be  added  to  the 
number  of  foreign  matters. 

Besides  being  impure  through  admixtures  of  vegetable  origin,  the 
grain  acquires  impurities  of  organic  and  mineral  substances,  and  particles 
of  metals.  The  method  of  production,  storage,  and  transportation  of  corn 
make  the  admixture  of  particles  of  straw,  empty  cobs,  stones,  dust  and 
dirt  that  cover  the  grains,  small  stones,  and  lumps  of  earth  inevitable. 
And  then  during  the  threshing  and  cleaning  of  grain  on  the  farm  more  or 
less  often  nails,  woodscrews,  nuts,  and  other  metal  parts  of  machinery 
fall  into  it. 

All  impurities  may  be  classified  in  three  groups  : 

(1)  Poisonous  admixtures  that  may  bring  about  an  empoisonment, 


CHAP,  in]  FLOUR    MILLING  59 

not  to  mention  the  deterioration  of  the  qualities  of  flour  (its  colour  and 
baking  qualities)  :   ergot,  cockle,  smut,  &c.,  pertain  to  this  class. 

(2)  Impurities  reducing  the  quality  of  flour.     Here  we  find  the  seeds 
of  non-poisonous  plants,  dust,  and  dirt. 

(3)  Impurities  that  may  do  some  damage  to  the  machinery,  e.g.  rapid 
wearing  out  of  sieves,  breakage  of  parts  of  the  machinery,  &c.     Stones 
and  pieces  of  metal  form  this  group. 

Now,  if  the  mill  is  to  yield  a  wholesome  product  of  good  quality,  and 
the  milling  machinery  is  to  be  set  in  normal  working  condition,  the  grain 
should  be  freed  of  all  this  foreign  matter. 

The  impurities  we  have  been  examining  usually  differ  from  the  sound 
product  by  one,  or  several  tokens  conjointly,  of  the  following  categories  : 
(1)  size,  (2)  specific  gravity,  (-3)  shape,  (4)  natural  peculiarity  of  the  ad- 
mixture. The  machine,  designed  for  the  extraction  of  foreign  bodies 
out  of  the  grain,  is  constructed  in  accordance  with  the  particular  manner 
in  which  the  impurities  differ  from  the  main  product.  Thus  four  types 
of  machinery,  each  taking  advantage  of  the  peculiar  differences  of  the 
admixtures,  have  been  evolved.  But  often  the  separation  of  the  grain, 
and  the  extraneous  bodies  differing  from  it  in  size  and  specific  gravity, 
is  combined  in  one  machine. 


II 

EXTRACTION  OF  PIECES  or  METAL  FROM  THE  STOCK 

Magnetic  Separators. — Before  feeding  the  grain  into  a  machine  all 
pieces  of  metal,  that  might  damage  the  working  parts  of  the  machine, 
must  be  extracted.  These  pieces  being  exclusively  of  iron  or  steel,  their 
extraction  is  based  on  the  property  of  the  magnet  to  attract  and  detain 
both  metals. 

A  magnetic  apparatus  adapted  for  that  purpose  is  shown  in  its 
simplest  form  in  Fig.  44.  It  consists  of  two  cast-iron  frames  C,  between 
which  a  cast-iron  box  D  is  placed.  The  frames  and  the  box  are  bolted 
together.  In  the  box  is  set  a  row  of  magnets,  their  poles  a  and  6  coming 
out  on  the  surface,  of  the  cast-iron  or  timber  tapering  plank  E.  The 
poles  a  and  b  are  disconnected  by  an  insolated  interlayer.  On  the 
plank  E  is  placed  a  cast-iron  or  timber  feed-hopper  A  with  a  gate  B, 
by  the  lifting  and  dropping  of  which  the  flow  of  grain  may  be  regulated. 
The  grain  is  poured  in  as  shown  by  the  arrow  S  and,  falling  through  the 
lower  crevice  between  the  gate  B  and  the  magnet  table  E  (arrow  S), 


60 


FLOUR    MILLING 


[CHAP,  in 
From  time  to  time 


leaves  the  iron  and  steel  pieces  on  the  magnet  line, 
these  admixtures  are  removed  by  hand. 

This  is  the  most  simple  apparatus,  though  sometimes  a  still  plainer 
appliance  is  used.  Horseshoe  magnets  of  the  common  kind  are  in- 
serted into  corresponding  spouts  down  which  the  grain  passes.  Usually 


FIG.  44. 


FIG.  45. 


a  wooden  stopper,  with  three  to  four  magnets  set  into  it,  is  fitted  into  a 
hole  in  the  spout  (Fig.  45).  At  intervals  the  stopper  is  taken  out,  and 
the  metal  particles  attracted  by  the  magnets  removed. 

The  removal  of  the  particles  detained  by  the  magnet  offers  some 
inconvenience,  demanding  constant  attention  from  a  workman  occupied 

on  other  machines.  There- 
fore another  type  of  mag- 
netic apparatus,  removing  the 
iron  particles  automatically,  is 
in  use.  Such  an  apparatus, 
from  Howes'  factory  in 
America,  is  represented  in 
Fig.  46.  The  whole  apparatus 
is  of  timber.  The  arrangement 
of  the  magnet  is  the  same 
as  in  the  simple  apparatus. 
But  here  cast-iron  scrapers  r 
set  on  an  endless  belt  (other  factories  make  a  chain-gearing)  pass  over 
the  magnet  surface.  These  scrapers  catch  up  the  iron  particles  stuck 
to  the  magnets  and  throw  them  into  the  bucket  E.  The  belt  is  driven 
by  a  pulley  t,  the  axle  of  which,  passing  through  the  feed-hopper, 
communicates  the  rotation  to  the  belt  pulley  n  with  the  aid  of  a  bevel 
gearing  k.  By  means  of  gears  8-8,  on  the  left-hand  side  of  the 
apparatus,  a  feed  roll  in  the  hopper  is  brought  into  play.  The  taper 
of  the  hopper  gate  is  regulated  by  screw  nuts  b-b,  thus  altering  the 


FIG.  46. 


CHAP.    Ill 


FLOUR   MILLING 


61 


feed   opening  between  the  roll  and  the  gate.      The  belt  R  is  tightened 
and  loosened  by  screw-nuts  g-g. 

The  number  of  revolutions  the  belt  of  such  an  apparatus  performs  per 
minute  is  between  15  and  25,  its  capacity  9  to  16'5  tons  per  hour,  accord- 
ing to  the  size  of  the  apparatus.  One  of  the  defects  of  this  apparatus  is 
that  the  scrapers  carry  some  grain  away  and  interrupt  its  even  flow. 

Besides  the  magnetic  apparatus  just  examined,  there  are  other 
apparatus  with  a  revolving  working  magnet,  and  with  an  electro 
magnet,  but  those  of  the  latter  kind  are  rather  complicated  in  construc- 
tion, and  are  seldom  used  in  mills,  since  the  simple  apparatus  works 
satisfactorily. 

The  capacity  of  the  simple  magnet  apparatus  varies  between  3'5  cwt. 
and  4'5  tons,  depending  on  its  size. 
A  magnetic  separator  with  revolv- 
ing magnets  is  shown  in  Fig.  47. 

The  magnets  are  enclosed  in 
the  cylinder  A  with  a  worm-wheel 
E  which  couples  with  the  worm  D 
fixed  on  the  axle  of  the  belt-pulleys 
(loose  and  fast)  T.  The  flat  sur- 
face of  the  cylinder  containing  the 
magnet  B  coincides  with  the  surface  of  the  spout,  where  a  hole  corre- 
sponding in  size  with  the  area  of  the  working  surface  of  the  magnet  is 
cut.  The  product  flowing  along  the  spout,  the  iron  particles  stick  to  the 
magnets,  which  are  then  scraped  off  with  bar  F  and  fall  out  through 
the  channel  a.  A  link  mechanism  C  serves  for  setting  the  magnet. 


FIG.  47. 


Ill 

SEPARATION  OF  LARGE  AND  SMALL  IMPURITIES 
1.  Separation  according  to  Size 

Sifting. — Previously  to  the  further  cleaning  of  grain,  a  product  has 
to  be  obtained  of  an  approximately  equal  size,  i.e.  a  product  of  which 
all  the  measurements  would  be  correspondingly  equal.  The  working 
surfaces  serving  to  that  purpose  are  the  sieves. 

As  shown  in  Fig.  48,  there  are  sieves  either  of  woven  iron,  steel, 
copper  or  bronze  wire,  or  of  a  perforated  sheet  of  metal. 

When  a  mass  of  corn  passes  over  such  a  sifting  surface,  the  separate 
grains  will  fall  through  the  s^eve  when  the  meshes  are  slightly  larger  than 


62 


FLOUR   MILLING 


[CHAP.*  m 


the  grains.  The  larger  matter  rolls  off  the  sieve.  In  this  manner  the 
throughs  supply  the  grain,  while  the  overtails  consist  of  the  larger 
impurities. 

The  removal  of  the  smaller  impurities  is  attained  by  rocking  the 
grain  on  a  sieve  of  which  the  meshes  are  smaller  than  the  smallest  grains. 
In  this  case  the  grain  tails  over,  and  the  small  matter  dresses  through. 

Before  passing  on  to  the  construction  of  the  machines  separating  the 
impure  matter  from  the  grain  by  sifting,  the  sizes  of  the  meshes  and 
the  numeration  of  cloths  have  to  be  explained. 

The  sizes  of  the  square  meshes  in  wire  sieves  are  defined  by  the  number 
of  cloth  which,  in  its  turn,  is  defined  according  to  the  number  of  wire 
threads  to  the  linear  inch.  If  the  number  of  the  sieve  is  6,  the  number 


FIG.  48. 


of  threads  is  6,  forming  36  meshes  to  a  square  inch.  No.  40  corresponds 
to  40  threads  and  1600  meshes,  &c.  It  is  to  be  noted,  however,  that 
the  reckoning  is  made  in  English  inches,  25  mm.  (in  England  and  in 
America),  Viennese  inches,  26  mm.  (in  Austria,  Hungary,  and  Germany), 
and  French  inches,  27  mm.  (in  France).  This  must  be  kept  in  view, 
when  selecting  fine  sieves,  No.  42  and  upwards,  from  various  factories. 

Besides  that,  the  thickness  of  wire  plays  a  prominent  part  in  the 
definition  of  the  size  of  the  cloth-meshes.  Generally  speaking,  the 
diameter  of  the  wire  varies  between  2J  and  0*1  mm.  Within  the  bounds 
of  Nos.  1  and  8  the  diameter  of  the  wire  does  not  vary  (in  No.  8  it  is 
0*5  to  0'65  mm.)  ;  outside  of  that  limit  it  may  differ.  For  this  reason 
the  density  of  the  cloth  is  greater  or  smaller,  which  is  reflected  in  the 
number  of  the  cloth,  though  the  meshes  be  of  the  same  size.  For 
instance,  No.  16,  a  cloth  of  greater  density,  corresponds  to  the  finer 
No.  20,  the  meshes  of  the  two  cloths  being  equal,  but  those  of  No.  20 


CHAP,  in]  FLOUR   MILLING  63 

exceeding  No.  16  in  their  number.     The  density  of  the  cloth  is  usually 
defined  by  the  weight  of  a  square  yard  or  metre. 

Nos.  1  to  8  are  applied  for  sorting  away  the  matter  larger  than  the 
grain,  of  which  Nos.  1,2,  and  3  are  used  in  front  of  the  primary  storage 
bins,  which  receive  the  grain  to  be  fed  into  the  mill.  These  sieves  detain 
large  stones,  chips  of  wood,  strings,  &c.  on  their  surface.  Nos.  4  to  8 
are  set  in  sifting  machines  where  the  sieves  separate  the  smaller  matter  as 
screenings,  the  grain  falling  through.  The  rest  of  the  numbers  of  wire 
cloths  above  8  keep  tail  over  the  grain,  and  let  the  fine  impurities 
through.  . » 

As  to  the  quantity  of  numbers  of  cloths  for  cleaning  the  grain,  in 
Germany  and  Austria-Hungary  forty  are  in  use,  beginning  with  the 
4th,  and  ending  with  the  75th.  These  numbers  are  arranged  in  the 
following  way  :  from  4th  to  26th  a  successive  increase  by  one  number  ; 
28th  to  46th,  by  two  ;  50th  to  70th,  by  four  ;  and  the  last  is  No.  75. 
The  Russian  factories  produce  generally  with  the  difference  of  one  the 
Nos.  1  to  8,  of  two  Nos.  10  to  28,  and  of  four  Nos.  32  to  60. 

In  Russia,  besides  the  numeration  to  the  inch,  there  exists  a  numera- 
tion to  the  vershok,  and  according  to  the  number  of  threads.  It  is 
adopted  here  and  there  on  the  Volga  and  in  the  central  region.  It  is 
advisable,  however,  to  keep  to  the  inch  numeration,  more  especially 
as  the  vershok  numeration  is  quoted  only  by  the  peasant  hand  workers 
in  the  government  of  Nijni-Novgorod. 

Speaking  of  perforated  sheet-iron  sieves,  the  fact  is  to  be  pointed  out 
that  their  numeration  is  exactly  the  reverse  of  that  adopted  in  woven- 
wire  clothing.  No.  1  is  the  sieve  with  the  finest  meshes,  |  mm.  in 
diameter,  and  No.  24  has  the  largest,  25  mm.  in  diameter.  There  are 
twenty-four  numbers,  No.  1  containing  the  greatest  quantity  of  meshes, 
1600  to  2025  to  a  square  inch.  The  shape  of  the  meshes  is  mostly  round, 
though  rectangular  ones  are  also  made. 


(i.)  The  Construction  of  Sifting  Machines 

During  the  sifting  process  the  product  must  be  made  to  travel  over  the 
bolting  surface.  This  is  done  by  means  of  moving  sieves,  which  compel 
the  grain  to  travel  in  the  direction  defined  by  the  kind  of  motion  peculiar 
to  the  sifting  surface.  On  examining  the  various  constructions  of  the 
machines,  we  may  divide  them  into  two  groups  in  respect  of  the  kind  of 
motion  of  the  sieves:  (1)  machines  with  vibratory  motion,  and  (2)  with 
rotary  motion. 


64 


FLOUR   MILLING 


[CHAP,  in 


FIG.  49. 


The  sieve  in  the  old  German  mill  (Fig.  28,  G]  may  be  regarded  as  the 
most  primitively  constructed  machine  of  the  first  type  that  can  be  used 
for  grain  cleaning.  Sieves  of  that  kind  are  set  at  a  slight  angle  to  the 
horizontal  plane.  When  the  sieve  frame  moves  in  a  longitudinal-reci- 
procal direction,  the  grain  is  displaced  by  force  of  inertia,  the  movement 
of  the  sieve  being  straight,  parallel  to  the  axis  of  oscillation.  When 

the  sieve  moves  cross  ways, 
the  grain  travels  in  a  zigzag 
line. 

A  comparison  of  the  two 
methods  of  moving  the  pro- 
duct over  the  sieve  persuades 
us  that  the  second  is  prefer- 
able, as  travelling  in  a  zigzag 
way  the  stock  remains  on 
the  working  surface  a  longer 
while,  and  the  separation  is 
more  perfect. 

"Eclipse  "  Bolter  of  Nordyke  &  Harmon  Co. — The  "Eclipse  "  bolter 
of  the  American  factory  of  Nordyke  &  Marmon  Co.  (Fig.  49)  presents  a 
simple  and  original  construction  of  a  sieve  with  longitudinal  oscillations. 
A  wooden  box  D  has  at  its  upper  end  a  receiving  hopper  A.  Two  sieve 
trays  B  are  fixed  in  the  box.  The  frame  is  set  on  four  U-shaped  springs  a 
and  is  oscillated  by  a  connecting  rod  b,  communicating  with  the  crank 
rod  of  the  driving  shaft.  C  are  the 
spouts  delivering  the  product  and 
small  impurities.  The  overtails  of 
the  upper  sieve  is  the  large  refuse. 
The  number  of  revolutions  is  450  per 
minute,  the  capacity  of  the  machine 
6  to  18  cwt.  per  hour. 

Reel-separators. — Machines  extracting  foreign  matter  by  bolting,  but 
with  their  working  surfaces  revolving,  are  called  reel-separators.  It  has 
already  been  mentioned  that  they  are  an  American  invention,  and  the 
simplest  form  of  that  machine  was  examined  on  p.  25,  Fig.  26.  The 
fundamental  principle  of  its  construction  is  the  same  to-day.  Besides 
the  use  of  the  round  reel-separator,  practical  flour  milling  has  introduced 
hexagonal  reels  into  the  industry,  by  reason  of  their  simple  construc- 
tion and  cheapness. 

A  reel-separator  of  the  most  simple  kind  (Fig.  50)  is  generally  a  timber 


FIG.  50. 


CHAP,  in]  FLOUR   MILLING  65 

hexagon  shell  A,  1250  to  3500  mm.  long,  its  diagonal  measurements 
350  to  1000  mm.,  covered  with  bolting  cloth  and  placed  in  a  timber 
chamber  B,  its  axis  inclined  at  an  angle  of  O'OS  to  O'l  to  the  horizon. 
The  reel-shaft  is  mounted  on  bearings  p,  outside  the  chamber.  The  grain 
flows  to  the  reel-separators  through  a  spout  N,  and  on  this  side  the  separa- 
tor is  sheltered  by  a  lid  H  revolving  with  the  reel-separators  conjointly. 
A  round  cover  0,  with  an  aperture  F,  for  the  passage  of  grain,  is  fixed  to 
the  interior  wall  of  the  chamber  and  is  stationary.  Between  H  and  G 
there  is  a  small  clearance,  besides  an  opening  with  a  clearance  in  G  for  the 
reel  shaft.  The  right  end  of  the  reel-separators  remains  open.  In  the 
sides  of  the  chamber  there  are  apertures  for  inspection,  closed  with  solid 
timber  gates  or  frames  clothed  with  linen.  The  reel-separator  is  operated 
by  a  bevel  gearing  C,  and  the  worm  conveyor  S  by  a  belt  (sometimes 
geared)  drive  on  belt-pulleys  D  Dv  The  head  of  the  reel-separator  (the 
inlet  of  the  product)  is  generally  clothed  with  one.  two,  or  three  num- 
bers for  sifting  the  small  matter,  the  tail  part  (outlet  of  the  product) 
with  cloths  with  larger  meshes  for  the  discharge  of  the  grain.  The  work 
is  performed  in  the  following  manner  :  the  grain  is  fed  through  N  into 
the  rotating  reel-separator,  which  being  inclined,  it  travels  in  a  zigzag 
line  towards  t.  The  small  impurities,  passing  to  the  lower  part  of  chamber 
B,  are  discharged  by  the  worm  S  through  the  opening  a.  The  grain  flows 
into  the  conveyor  box  E,  and  runs  out  into  6,  while  the  large  impurities 
fall  out  as  refuse  through  the  opening  c. 

A  plainer  reel  has  no  conveyor,  and  the  lower  part  of  the  chamber  is 
divided  into  hoppers  (outlined  in  dots)  delivering  the  small  impurities 
through  openings  a  and  a2. 

Figs.  51  (longitudinal  section)  and  52  (cross  section)  represent  a 
reel-separator  constructed  of  metal  (cast-iron  frame  and  iron  hoppers) 
by  Thomas  Robinson  &  Son,  Rochdale,  England.  No  conveyor  is 
adopted  here  ;  the  dust,  sand,  &c.,  small  impurities  falling  automatically 
out  of  the  first  conical  hopper,  the  grain  out  of  the  second,  while  the  large 
refuse  passes  out  the  same  way  as  in  the  preceding  reel- separator. 

The  simplest  kind  of  a  round  reel-separator  with  a  timber  frame  and 
boxes  is  shown  in  Fig.  53.  The  reel  is  clothed  with  three  cloths  of 
various  numbers.  Two  sections,  A-A,  for  small  refuse,  sand  and  dust, 
are  clothed  with  No.  14 ;  two  other  sections,  B-B,  for  larger  matter  and 
very  small  grain,  have  Nos.  10  to  12 ;  the  last  two  sections,  C-C,  for  the 
passage  of  grain,  Nos.  5  to  6.  The  large  impurities  tail  over.  The 
product  moves  in  the  direction  indicated  by  the  arrow.  The  hopper  D 
receives  the  small  impurities,  E  the  medium,  and  F  the  pure  grain.  The 


66 


FLOUR   MILLING 


[CHAP,  m 

doors  are  removable  from  the  side  walls  of  the  reel-chamber  ;  one  of  them, 

6r,  is  shown  in  the  drawing.     The  cylindrical  reel-separator  generally  con- 

sists of  two  semi-cylinders,  so  as  to  afford  the  possibility  of  their  clothing. 

Sometimes  the  clothing  used  for  reel-separators  is  of  perforated  sheet- 


iron  with  round  or  rectangular  holes.  The  reel-separator  in  Fig.  54  is 
furnished  with  three  sieves,  of  which  A  has  rectangular  and  round  holes, 
B  only  round,  and  C  only  rectangular.  The  product  is  fed  as  indicated  by 
arrow  S.  In  section  A  the  throughs  are  small  impurities,  and  long  but 
thin  seeds  (of  oats,  rye,  shrivelled  grains  in  wheat  cleaning)  ;  section  B 


CHAP,  m]  FLOUR   MILLING  67 

gives  only  the  small  refuse  as  throughs,  and  the  clean  grain  is  sifted  through 
in  section  C.  The  larger  refuse  constitutes  the  overtails.  In  this  way, 
m  the  first  part  of  this  reel-separator,  impurities  differing  in  size  as  well 
as  in  shape  (oats,  wild  oats,  rye)  are  separated  away.  Another  type  of 
machine,  however,  for  sorting  the  grain  according  to  shape  remains  to  be 
noted.  Therefore  the  use  of  reel-separators  supplied  with  these  covers 
is  expedient  only  where  a  simplification  of  the  grain-cleaning  pro- 
cess is  unavoidable  from  considerations  of  economy,  and  the  grain- 
cleaning  department  is  deprived  of  machinery  sorting  the  grain  according 
to  shape. 

However,  an  outline  may  be  given  of  the  modern  type  of  reel-separa- 


tors, which  are  mainly  used  on  mills  for  separating  the  large  and  small 
grain,  though  also  capable  of  sorting  the  seeds  of  other  plants  away 
from  the  chief  bulk  of  product  to  be  milled.  Fig.  55  represents  a  cylindrical 
grader  reel  from  the  factory  formerly  known  as  "  Bros.  Seek,"  in 
Dresden.  The  product  is  fed  into  the  receiving  spout,  and  falls  into  the 
reel,  covered  with  a  bolting  cLoth  with  rectangular  meshes.  (The  sieve 
next  to  cloth  A  is  removed.)  The  meshes  of  the  sieve  A  may  be  the  same 
throughout  the  whole  length  of  the  reel.  In  that  case  the  throughs  will 
be  the  small  grain  and  the  large  grain  will  remain  as  overtails.  If  half 
of  the  reel- separator  is  clothed  with  meshes  for  rye  and  oats  (when  wheat 
is  treated),  the  second  half  must  carry  meshes  for  small  wheat.  Then  tho 
box  containing  the  conveyor  C  will  have  two  discharge  spouts,  Zl  and  Z2. 


68 


FLOUR   MILLING 


[CHAP   in 

The  peculiarity  of  this  reel-separator  consists  in  its  being  furnished  with 
brushes  B  of  iron  wire.  These  brushes  revolve  and,  being  pressed  against  the 
cover  of  the  reel,  clear  the  meshes  of  the  grains  stuck  in  them.  The  reel- 
chamber  is  of  timber,  and  its  parts  of  metal.  T  are  timber  doors  (one 

is  off),  K  and  Kl  are  lids  for 
the  inspection  of  the  worm. 
The  reel-separator  is  driven 
by  a  bevel  gearing,  .and  the 
worm  by  means  of  a  belt-drive 
on  pulleys  b  and  a. 

Vibro-motor     Plansifters.  - 
The    small     capacity     of     the 
reel,  and  the  "detrimental  effect 
FIG.  55.      "  °f  ^ne  inertia  of  the   mass    of 

machinery    with     flat     bolting 

trays  reciprocating,  compelled  builders  to  design  a  type  of  machine 
supplied  with  flat  sieves.  The  first  machine  of  that  style  was  dis- 
played at  the  Universal  Exhibition  in  Vienna,  1873,  by  a  miller 
from  Pfalz,  Johann  Pfoltz.1  The  principle  of  operation  in  this  machine, 
which  afforded  K.  Haggenmacher  later  a  basis  for  the  flat-bolter,  in- 
vented by  him  in  1888,  is  the 
following  :  a  flat  sieve  s  (Fig.  56) 
is  suspended  from  the  ceiling  by 
means  of  four  rods,  a,  b,  c,  and  d, 
and  is  connected  with  a  rotating 
crank  shaft  A.  The  product 
falling  on  the  tray  is  bolted,  while 
travelling  in  a  gyratory  line. 
A  progressive  displacing  of  the 
product  is  attained  by  an  in- 
clination of  the  tray,  which  is  the 
method  adopted  by  the  firm  of 
G.  Luther  in  their  aspirators  of 
latest  type,  or  by  means  of  guiding  scrapers  as  suggested  by  Haggenmacher 
in  his  flat  bolter.  If  a  horizontal  flat-bolting  frame  is  divided  by  cross 
partitions  1,2,  3,  .  .  .  as  shown  in  Fig.  57,  the  product  will  travel  pro- 
gressively as  indicated  by  the  arrow  r,  the  partitions  stopping  it  half-way 
and  propelling  it  to  run  another  circle.  Were  the  frame  not  furnished  with 


FlG- 


1  In  1878  another  inventor,  Pieter  van  Gelder,  patented  a  flat  bolter  in  England,  based  on 
the  same  principle. 


CHAP.    Ill] 


FLOUR   MILLING 


69 

partitions,   the    product    would    describe    full   circles,    as   shown  in  0, 
remaining  always  on  one  and  the  same  spot. 

Flat  grain-bolters  of  the  Haggenmacher  type  are  built  at  the 
English  works  of  Thos.  Robinson  (Rochdale).  The  construction  of 
machinery  with  flat  sieves  will 
be  examined  later. 

The  construction  of  the 
machinery  we  have  become 
acquainted  with  enables  us  to 
extract  the  large  and  small 
impurities  and  sort  the  grain  in  respect  to  its  size,  which  is  of 
great  importance  to  the  further  cleaning  processes,  to  be  considered 
later.  Therefore  it  follows  out  of  the  very  idea  of  cleaning,  that  the 
positions  and  numbers  of  sieves  must  be  as  shown  below  (English 
notation). 


FIG.  57. 


Grain 


No.  14 

No.  12 

Nos.  8-10 

Nos.  5-6 

Throughs    |    Throughs    |    Throughs 
Small  Medium  Small  Normal 

impurities,      impurities.  grain.  grain. 


Tailing  over  of  large 
impurities. 


In  this  way,  first  of  all  on  covers  Nos.  14  and  12,  small  impurities, 
sand  and  dust,  are  sifted  through ;  on  cover  No.  8  or  10,  small  grain ; 
on  cloth  No.  5  or  6,  the  normal  grain,  the  large  impurities  being 
tailed  over. 

If  the  grain  contains  a  large  amount  of  impurities  (stones  particu- 
larly), to  save  the  covers  Nos.  14,  12  and  8,  10  from  the  wear  and  tear, 
a  separate  reel-separator  may  be  fitted  up  for  separating  the  large  refuse, 
and  another  for  cleaning  the  grain  of  small  impurities  and  sorting  it. 
Then  the  scheme  of  cleaning  is  : 


No.  5 

No. 

•  1 

Throughs 

1 
Grain 


L 


No.  14 

No.  12 

Nos.  8-10 

•Discharge  of  normal 
grain. 


Small  Medium  Small 

impurities,      impurities.          grain. 


70 


FLOUR    MILLING 


[CHAP,  in 


Both  the  schemes  refer  to  grain  cleaning  on  reel- separators.  The 
system  of  cleaning  on  sieve-separators,  and  the  order  of  the  numbers, 
will  be  examined  later. 


(ii.)  The  Quality  and  the  Quantity  of  the  Work  of  Sieve-Bolters 

Let  us  now  compare  the  quality  and  quantity  of  work  of  flat  sieves 
and  two  types  of  reel-separators.  The  working  quality  is  defined  by  the 
uniformity  of  the  effect  resulting  from  the  operations  of  any  particular 
working  organ — the  bolting  surface,  in  this  case. 

Figs.    58,    59,    and   60   represent   a    cross   section   of  reel-separators 


FIG.  58. 


FIG.  59. 


and  part  of  a  hexagon  reel-separator.  We  see  in  Figs.  59  and  60  that 
the  full  working  surface  of  the  reel-separators  is  not  utilised  in  the 
operations,  and  Fig.  59  illustrates  the  fact  that  not  all  the  sieve 
actually  bolting  is  capable  of  doing  equal  work.  Fig.  59  exhibits 
the  small  grain  6  and  impurities  a  that  are  to  pass  through,  on  the 
lower  part  of  the  hexagon  reel  or  flat  sieve,  and  on  the  side  wall 
of  the  reel.  In  the  first  position,  a  and  b  will  easily  pass  through 
the  meshes  of  the  sieve,  if  fitting  them ;  in  the  second  position, 
they  cannot  fall  through,  being  wedged  in  between  the  facets  of  the 
mesh,  as  the  area  of  the  passage  here,  projected  on  the  horizontal  plane, 
is  diminished  in  proportion  to  the  angle  of  inclination  of  the  reel. 
Those  impurities  must  be  again  thrown  on  the  horizontal  plane  of 
the  bolter,  to  attain  the  position  favourable  to  sifting.  It  is  clear, 
consequently,  that  not  every  part  of  the  working  surface  produces 
the  same  effect,  and  thus  the  capacity  of  the  machine  is  diminished.  If  we 


CHAP.    Ill] 


FLOUR   MILLING 


71 


have  a  flat  sieve  with  a  fixed  incline,  the  impurities  passing  through 
the  layer  of  grain  to  the  meshes  will  necessarily  pass  through  them. 

An  examination  of  the  distribution  and  motion  of  the  product 
in  reels  shows  firstly  that  only  £  to  J  of  the  sifting  surface  is  in 
actually  sifting;1  secondly,  the  bulk  of  product  Q  (hexagon  reel), 
thrown  off  the  side- walls,  when  the  reel  is  in  rotation,  hits  the  lower 
wall,  and  wears  it  out  more  rapidly,  though  effecting  a  more  energetic 
sifting.  If,  on  the  other  hand,  the  bolting  is  performed  on  a  flat  sieve, 
firstly  the  whole  surface  is  utilised,  and  secondly,  all  the  parts  of  the 
working  surface  are  subject  to  the  same  wear  and  tear,  as  the  grain 
travels  in  a  compact  mass 
over  the  whole  sieve. 

These  are  the  reasons 
why,  in  regard  to  their 
operating  qualities,  capacity, 
and  wear,  flat  sieves  are  to 
be  preferred  to  other  bolt- 
ers. Besides  these  advan- 
tages, flat  sifters  are  much 
more  compact,  and  economy 
of  space  plays  a  great  part 
in  the  choice  of  machin- 
ery. The  only  advantage 
of  reel-separators  is  their 
comparative  cheapness  and 
simplicity  of  construction. 

No  clearly  definite  capacity  of  flat  sieves  and  reel-separators  per 
unit  of  surface  may  be  spoken  of,  as  flour  milling  technics  have  as  yet 
no  records  of  accurate  tests.  That  is  the  cause  of  contradictions 
in  the  data  of  German  authors  (Kick,  Wiebe,  Pappenheim,  Ketten- 
bach,  &c.),  and  we  shall  not  quote  them.  It  is  to  be  kept  in  mind 
that  the  capacity  of  the  bolters  depends  on  the  amount  of  impurities 
mixed  with  the  product,  a  fact  never  alluded  to  by  the  above-mentioned 
authors. 

Practical  experience  has  shown  that  the  capacity  of  flat  sieves  is 
two  to  four  times  as  great  as  that  of  reel-separators.  As  to  the  cylindrical 
reels  their  sifting  capacity  for  various  sizes  is  defined  by  the  following 

1  Some  authors  accept  only  |  of  the  surface  in  the  hexagon  bolter  (one  facet).  However, 
we  cannot  agree  with  that,  for  bolting  is  effected  by  the  lower  side  too  in  consequence  of  the 
impetus  acquired  by  the  stock  Q  when  thrown  about. 


FIG.  60. 


72 


FLOUR    MILLING 


[CHAP,  in 


table,  giving  the  average  of  data  from  European  and  American  works 
verified  in  practice. 

The  incline  of  the  reel  is  80  mm.  to  1000  of  length. 

TABLE  X 


Dimensions  of  Cylinder. 

Number  of 

Capacity  per 

Nos. 

Revolutions  per 
Minute. 

Hour  in 
Kilogrammes. 

Diameter. 

Length. 

1 

350 

1250                 34 

250 

2 

400 

1500                 31 

450 

3 

450 

1750 

28 

625 

4 

500 

2000 

26 

825 

5 

500 

2250 

24 

1000 

6 

600 

2500 

22 

1250 

7 

700 

2750 

20 

1850 

8 

800 

3000 

18 

2500 

9 

900 

3250 

16 

3100 

10 

1000 

3500 

15 

3500 

The  first  three  numbers  of  reels  have  but  three  numbers  of  cloths 
each.  By  means  of  the  first  sheet,  the  reels  separate  the  dust,  sand,  &c. 
(sieve  No.  14).  The  second  bolts  the  small  refuse  (No.  12)  ;  in  the  third 
(Nos.  5  and  6)  the  grain  passes  through,  the  large  impurities  tailing  over. 
The  rest  of  the  numbers  of  reels,  i.e.  those  beginning  with  2000  mm. 
length  of  cylinder  upwards,  successfully  work  with  four  sheets  of 
cloth.  Here  the  throughs  consist  of  small  refuse  (Nos.  14  to  12),  small 
grain  (Nos.  10  to  8),  and  normal  grain  (Nos.  6  and  5),  while  the  large 
refuse  tails  over. 

(iii.)  Cleaning  according  to  Specific  Gravity  and  Size 
After  the  impurities  have  been  separated  away  by  bolting,  the  mass 
of  product,  though  uniform  in  size,  still  often  contains  foreign  matter  in 
the  shape  of  light  grains,  shells,  &c.,  which  have  to  be  extracted.  That 
is  done  by  winnowing  the  grain.  The  primitive  method  of  winnowing  is 
the  utilisation  of  the  natural  power  of  wind  on  peasant  farms,  where  the 
grain  is  thrown  up  with  shovels,  and  the  wind  carries  the  light  matter 
away.  If  machinery  is  used  for  that  purpose  an  air-current  is  artificially 
induced  by  fans. 

The  simplest  form  of  machine,  called  an  aspirator,  is  shown  in  Fig.  61. 
The  simple  separator  consists  of  a  chamber  A  with  a  fan  v.  The  lower 
part  of  the  chamber  ends  in  a  hopper  closed  by  a  balanced  valve  d. 
The  lid  of  the  chamber  carries  a  valve  e  opening  inwards,  also  counter- 


CHAP-  ni]  FLOUR    MILLING  73 

balanced.     The  grain  passing  down  the  spout  a  encounters  on  its  way 

in  6  a  current  of  air  aspirated  by  a  fan,  which  removes  the  light  impurities. 

The  light  impurities  are  carried  to  the  chamber  A,  where  those  lightest  are 

ejected  by  the  fan,  the  less  light  particles 

falling  into  the   hopper.      When   a  large 

quantity  of    refuse    has  collected  in  the 

hopper,  the  valve  d  is  pushed  open   by 

its    weight,     and    after     discharging    it, 

closes  again.       The  valve  e  automatically 

admits  air  into  the  rarefied  space  in  the 

chamber.     If    the    fan  works  too  power-  FlG-  61< 

fully,  then  the  current  of  air  takes  the  normal .  grains  away  with  it. 
With  a  view  to  a   more  effective  cleaning  A.  Fisher  suggested  the 

construction  of  an  aspirator  with  a  triple  aspiration.     Through  the  feed 

tube  a  (Fig.  62),  in  the  direction  of  the  arrow  S,  the  grain  flows  on  to  a 

spout  furnished  with  three  partitions,  the  height  of  which  may  be  regulated 

by  the  screw  d.  The  air-current,  passing 
up  (arrows  r),  encounters  the  stock  thrice, 
and  removes  the  light  matter,  which  is 
carried  through  c  to  a  chamber  similar  to 
the  one  just  described.  The  heavier  ex- 
traneous matter  falls  into  the  spout  d  by 
the  way  of  slt  s2,  and  s&  and  is  discharged 
into  a  sack.  The  defect  of  Fisher's  aspirator 
lies  in  the  fact  that  a  mass  intermixed  to 
a  greater  extent  with  light  impurities  meets 
a  current  of  air  weakened  and  dirtied  by  its 
preceding  work. 

The  manifold  exhaust,  based  on  the 
principle  of  Fig.  63,  is  much  more  effective. 
In  that  machine,  the  grain  discharged  into 
the  feeder  A  (arrow  S)  undergoes  a  quad- 
ruple aspiration,  with  pure  air  each  time. 
FlG  62  The  construction  of  this  machine  is  very 

simple.     A  timber  chamber  B,  containing  a 

fan  F,  is  baffled  by  inclined  partitions,  which  form  a  spout  for  the 
grain  'delivered  through  M  after  the  aspiration.  The  upper  wall  of 
the  chamber  carries  an  automatic  valve  k,  regulating  the  rarefication 
of  the  air  in  B.  The  hopper  D  receiving  the  heavy  screenings  ends  in 
valves  a-b,  which,  opening  under  the  pressure  of  the  mass  of  impurities. 


74 


FLOUR   MILLING 


[CHAP,  in 


discharge  them.     The  lighter  refuse  falls  into  box  Dt  and  is  conveyed 

out  by  c  and  d,  while  the  lightest  matter  is  ejected  with  the  air  current 

by  the  fan. 

Robinson's  Aspirator.  —  For 
the  removal  of  light  extraneous 
matter,  there  exists  machinery 
constructed  on  the  principle 
of  utilising  centrifugal  power. 
Of  the  novel  types  of  such 
machinery  Robinson's  aspirator 
must  be  described  (Fig.  64). 
The  grain  falls  through  the 
feeder  and  down  a  spout,  run- 
ning vertically  through  the 
exhaust  chamber,  on  to  a  revol- 
ving cast-iron  disc.  From  the 
disc,  it  is  distributed  fan-wise, 

and  then  encounters  a  current  of  aspirated  air,  which  carries  the  light 

matter  away,  and  then  conveys  it  down  a  spout  to  its  exit.     The  heavier 

refuse,  encountering  a  deflecting  partition  on  its  way,  falls  into  the  box, 

while     the    lighter     matter 

passes     through     the     fan 

either  to  the  dust  collector 

or  out  of  the  mill.     In  this 

aspirator  the  feed  spout  may 

be   raised  and  dropped  by 

means   of   a  lever-gear  and 

screw  for  regulating  the  flow 

(cross  section   between  the 

disc   and   the  spout).     The 

disc  runs  at  190  revolutions 

per  minute.     An  inspection- 

glass  is  fitted  in  the  top  of 

the  screenings  channel. 

The    capacity    of    this 

aspirator,  according  to  the  data  of  the  factory,  is  from  250  to  83  bushels 

per    hour,    corresponding    to    the    size    of    the    machine    (Nos.    1,    2, 

and  3). 

Robinson's  Cyclo-pneumatic  Separator.  —  Another  machine  of  Robin- 

son's, constructed  on  the  same  principle  and  connected  with  a  cyclone  for 


VALVC  4  QUADRAN7 


\    HAHDLt rOK 
TUJVS7IH6  LfHfTH 
\aFFCED3POUT.} 


FlG 


CHAP.    Ill] 


FLOUR    MILLING 


75 


collecting    light    impurities,    is    the    cyclo-pneumatic    separator.1    Here 
(Fig.  65)  the  disc  receiving  the  grain  is  esnclosed  in  the  cyclone  C,  and  the 
fan  is  above  the  cyclone.    The  fan  draws  the  air  out  of  the  cyclone  through 
a  passage  in  the  axis,  and 
impels  it  into  the  space  B, 
by    which   it    is    conducted 
through  a  side  aperture  into 
the   cyclone.     In   this   way, 
the  work   is   performed    by 
the    same     volume     of     air 
which  undergoes  purification 
in    space    B.     Part    of    the 
lighter  refuse  settles  on  the 
sides  of  the  cyclone,    owing 
to     centrifugal     force,     and 
sliding  down  the  incline,  on 
reaching  the  worm-conveyor, 
is    taken    to    the    discharge 
spout.  The  heavier  screenings 
are  delivered  to   the  worm- 
conveyor  out  of  the  chamber 
B.      The    light    and    heavy 
impurities     are     discharged 
into  one  spout  in  the  present 
case,  but  a  separate  passage 
for  either  can  be  afforded  by 
placing  another  spout  along 
the  route  of  the  worm-con- 
veyor before  the  outlet  for  the 
light  impurities  in  the  cyclone. 
The  cyclo-pneumatic  separ- 
ator's capacity  is  100  to  335 
bushels  per  hour. 

Horde's   .Combined     Ma- 
chine.— For  the  simultaneous 
extraction  of   foreign  bodies 
differing   in  size   and  specific  gravity,   machines   operating    by   sieves 
and   aspiration   are   constructed.      Horde's  separator  (Fig.  66)  belongs 

1  A  machine  of  a  similar  type,  Holt's  separator,  was  offered  some  twenty  years  ago,  but 
owing  to  the  defects  in  its  construction  it  did  not  succeed, 


FiG.  65. 


76 


FLOUR   MILLING 


[CHAP,  in 


to  the  simplest  class  of  combined  machine.  It  is  a  common 
separator,  on  the  top  of  which  a  frame  8  with  two  bolts  is  set  on  four 
flexible  timber  stands  t.  The  frame  is  reciprocated  by  means  of  two 
rods  r,  connected  with  a  crank-axle  u,  carrying  weights  rotating 

on  it,  the  object  of  which  is  to 
counterbalance  vibration  of  the 
bolting  frame.  The  grain  is  fed 
on  to  the  first  sieve,  No.  6,  which 
retains  the  large  impurities  and 
delivers  them  through  the  side- 
spouts  a-a. 

On  sieve  No.  9  the  grain  is 
separated  from  the  small  matter 
and  flows  down  the  spout  b  to 
the  expansion  chamber  A,  where 
it  undergoes  a  triple  aspiration 
i,  ilt  and  *2,  making  its  exit, 
cleaned,  through  c.  The  throughs 
from  No.  9  pass  down  sheet-iron 

J IG.    DO. 

bottoms  p-p    to    the    side-spout 

0.  Driven  by  a  stream  of  air  the  heavier  screenings  fall  into  the  hopper  d, 
and  thence  to  the  expansion  chamber  B,  where  they  are  fanned  once 
more  in  is  before  leaving  the  machine  through  e.  The  lightest  impurities 
are  drawn  in  by  the  fan  along  the  air- trunk  /,  and  ejected  with  the  air, 
while  the  medium  refuse 
travels  out  of  the  machine 
down  the  inclined  planes  /. 

The  defect  of  this  ma- 
chine is  identical  with  that 
of  Fisher's  separator,  i.e.  the 
first  aspiration  i  is  performed 
with  impure  air.  For  this 
reason  the  bolting  separator 
of  Fig.  67,  with  a  five-fold 
aspiration,  each  time  with  a  fresh  volume  of  air  s,  is  preferable.  The 
grain  is  delivered  through  the  spout  c,  the  heavy  refuse  falls  into  conveyor 
box  a,  mediums  into  6,  and  the  light  matter  passes  out  with  the  air. 

In  modern  machines  of  this  type  the  fan  generally  runs  at  500  to  600 
revolutions  per  minute,  the  crank  axle  at  250  to  300,  their  capacity  being 
40  to  165  bushels,  varying  with  the  size  of^the  machine, 


FIG.  67. 


.    Ill] 


FLOUR   MILLING 


T.  Robinson's  Separator. — In  mills  of  great  capacity  and  in  ware- 
houses, where  a  large  quantity  of  grain  has  to  be  cleaned,  Robinson's 
type  of  machinery  is  found.1  The  grain  flows  into  the  feeder  (Fig.  68), 
and  presses  open  with  its  weight  the  valve,  which  is  counterbalanced 
by  weights  on  shafts.  It 
passes  on  to  the  first  sieve 
of  perforated  steel,  No.  20 
(meshes  10  mm.  in  dia- 
meter), and  in  falling  on 
the  sieve  is  subjected  to 
the  effect  of  a  strong  cur- 
rent of  air,  which  carries 
away  all  light  extraneous 
matter.  The  tails  of  the 
first  sieve  are  large  im- 
purities, while  the  grain 
and  the  remaining  im- 
purities pass  to  the  second 
bolting  tray  with  two 
numbers  of  clothing,  14 
and  1 3 .  Here  the  medium 
impurities  are  separated 
away,  while  the  grain 
falling  through  is  bolted 
on  the  third  sieve,  No.  3, 
with  meshes  of  f  mm. 
On  the  third  sieve  the 
grain  is  sifted  off,  and  is 
then  exhausted  with  fresh 
air  in  the  discharge  spout ; 
the  throughs  here  consist 
of  fine  impurities.  The 
three  trays  are  enclosed 
in  one  common  box  which  is  suspended  from  the  frame  of  the 
machine  on  four  flat  steel  rods,  and  is  reciprocated  in  the  same  way 
as  the  trays  of  an  ordinary  separator.  The  air-draught  is  induced  by 
two  fans  running  at  about  600  revolutions  per  minute.  Light  impurities 

1  This  type  has  been  appropriated  from  its  American  constructors,  and  is  being  built,  with 
unimportant  variations,  by  all  large  European  works — Seek,  Daverio,  Luther,  Amme  Giesecke 
and  Konegen,  &c. 


FIG.  68. 


78  ^  FLOUR    MILLING  [CHAP,  in 

are  blown  through  the  fan  to  the  dust  collector,  while  the  heavy  refuse 
falls  into  hoppers  and  slides  out  down  inclined  spouts. 

The  main  shaft,  which  imparts  a  rocking  motion  to  the  sieve,  makes 
about  550  r.p.m. 

The  capacity  of  such  machines  varies  between  216  and  2400  cwt. 
per  hour. 

Aspirator  of  form.  Seek  Bros. — This  aspirator  is  generally  used  for 
cleaning  the  grain  to  be  kept  in  warehouses,  and  in  mills  of  a  large 
capacity.  Through  the  feeder  a  (Fig.  69),  the  grain  is  delivered  on  to 
the  first  sieve  with  large  meshes,  which  tails  over  the  coarse,  extrane- 
ous matter,  while  the  grain  falls  on  the  sieve  c  with  finer  meshes, 
which  remove  the  smaller  impurities,  such  as  corn-cobs,  straws, 
stones,  &c.,  which  pass  out  through  a  side-spout  d.  The  sifted  product 
is  then  bolted  on  sieve  e,  which  separates  the  still  smaller  impurities 
and  flows  in  a  thin,  even  stream  through  the  discharge  spout  /, 
where  it  is  exhausted  by  a  current  of  air,  and  freed  from  the  dust, 
chaff,  &c. 

When  entering  in  the  machine,  the  feed  is  subjected  to  the  action 
of  exhausts  gg,  which  suck  out  the  loose  dust,  before  it  is  passed  to 
the  sieves.  Owing  to  this,  the  machine,  when  in  operation,  produces 
no  dust.  The  cleanness  of  the  reverse  side  of  the  sieves  is  maintained  by 
automatic  brushes  hh  or  india-rubber  balls  which  are  distributed  over 
the  clothing,  and  the  trays  moving  from  side  to  side,  hit  the  perforated 
sheets,  thus  freeing  them  of  dust. 

The  feed  may  be  regulated,  and  is  performed  automatically,  viz. 
the  force  of  the  stream  varies  in  accordance  with  the  quantity  of  the 
stock  fed,  in  this  manner  preventing  any  stoppage,  and  continuously 
keeping  a  certain  amount  of  grain  in  the  hopper.  This  arrange- 
ment lacking,  the  bolting  surface  would  not  be  supplied  with  the  stock 
evenly  over  its  full  breadth,  thus  the  aspiration  would  be  inefficient. 

The  heavy  particles  of  dust  lifted  by  the  stream  of  air  collect  in  two 
chambers  ii,  whence  they  are  discharged  through  rocking  channels  kk, 
arranged  on  the  sieve.  The  fine  dust,  at  the  same  time,  is  driven  by  the 
fan  to  the  dust  collector. 

When  mounted,  the  machine  has  to  be  carefully  adjusted  by  means 
of  a  spirit-level.  By  means  of  weights  L,  adjustable  by  screws  placed 
at  the  mouth  of  the  feeder,  the  force  of  the  stream  of  stock  must  be 
regulated,  so  as  to  keep  the  hopper  continually  filled  to  three-fourths 
of  its  capacity.  The  same  is  to  be  said  of  the  regulation  of  the  product 
in  I,  when,  on  leaving  the  trays,  it  flows  into  the  suction  drum  at  the 


FLOUR   MILLING 


79 


CHAP.   Ill] 

exit.     At  the  feeding  and  the  discharge  apertures  the  air-draught  is  con- 
trolled by  means  of  valves  mm,  arranged  in  the  expansion  chamber, 


which  are  worked  from  the  outside  by  levers.  The  levers  are  adjusted 
in  their  places  by  means  of  screws.  In  addition,  a  more  satisfactory 
control  may  be  attained  by  means  of  two  timber  distributing  slide- 


80  FLOUR   MILLING  [CHAP,  ill 

valves  rtri,  set  in  the  partitions  between  the  refuse  collecting  chambers 
and  the  common  expansion  chamber  of  both  the  exhausts.  These 
slide-valves  may  be  reached  through  a  sheltered  aperture  in  the  middle 
of  the  upper  plank  of  the  aspirator.  The  slide-valves  must  never  be 
quite  closed. 

The  aspirator  can  only  be  adjusted  accurately  after  a  trial  operation. 
The  removal  of  all  light  impurities  from  the  stock  by  the  air-current  is 
to  be  aimed  at ;  the  good  particles  of  stock,  however,  should  not  be 
carried  to  the  refuse  chamber. 

The  aspirator  legs  are  connected  by  a  spout,  which  further  is 
connected  with  the  common  air-trunk.  The  trunk  opens  into  the  dust 
chamber,  or  communicates  with  some  dust-collector.  The  new  bore  of 
the  air- trunk  may  not  be  smaller  than  the  sum  of  the  bores  of  both  the 
aspirator  legs.  Any  slight  curves  of  the  air-trunk  must  be  made  with  as 
large  a  radius  as  possible. 

The  machine  is  worked  from  the  shaft  of  the  fan  making  570 
revolutions  per  minute  ;  by  means  of  belts  the  motion  is  transmitted  to  a 
crank-shaft  which  rocks  the  sieves,  and  runs  at  650  revolutions. 

The  capacity  of  such  machines  varies  between  60  and  2000  bushels  for 
warehouses,  and  20  to  620  bushels  per  hour  for  mills,  according  to  the  size 
of  the  machine. 

The  Zigzag  Separator. — In 'this  machine  (Fig.  70),  which  does  the 
same  work  as  the  preceding  one,  the  trays  are  arranged  in  a  zigzag 
line.  All  five  sieves  are  enclosed  in  a  common  box,  but  its  reciprocative 
motion  runs  athwart  the  direction  the  stock  travels.  We  shall  first 
follow  the  travel  of  the  stock,  and  then  compare  this  construction  with 
that  of  the  preceding  machine.  From  the  feed-hopper,  having  opened  the 
counterbalanced  slide,  and  exhausted  by  an  air  current,  the  grain  falls 
on  the  first  sieve  (longitudinal  section)  with  round  holes  (diameter  12  mm.), 
which  shakes  the  large  impurities  off  and  sifts  the  grain  and  other  matters 
through.  This  tray  is  rocked  longitudinally,  its  axis  being  perpendicular 
to  the  axes  of  sieves  2,  3,  and  4.  The  throughs  of  the  first  sieve  falling 
on  the  second  with  meshes  d  =  5  mm.  leave  the  large  impurities  of  the 
second  order  on  its  surface,  the  grain  and  smaller  screenings  passing  through 
to  a  plate,  lying  parallel  to  the  sieve,  and  are  conveyed  to  the  head  of  the 
third  tray.  The  third  sieve,  having  meshes  d=4:%  mm.,  retains  ex- 
traneous matters  of  the  third  order  in  size,  giving  as  throughs  the  rest  of 
the  stock,  which  collects  on  a  similar  plate  under  the  sieve,  which  in  a 
like  manner  conducts  the  product  to  the  head  of  the  fourth  sieve, 
meshes  d=4  mm. 


CHAP,  m] 


FLOUR   MILLING 


81 


Large  impurities  of  the  last  size  are  sifted  off  on  the  fourth  sieve, 
and  the  throughs  reach  the  fifth  sieve,  the  axis  of  which  is  set  perpen- 
dicularly to  those  of  the  preceding  sieves.  The  meshes  of  the  fifth  sieve 
are  d=2  mm.  It  tails  the  grain  over  and  bolts  small  refuse,  dust,  and 
sand.  The  grain  from  the  last  sieve  passes  through  the  exhaust  leg  to 
the  fan  and  is  freed  of  the  remaining  impurities  and  dust  (cross  section). 

In  comparing  this  machine  to  the  one  preceding  we  notice  that  the 
zigzag  arrangement  of  sieves  makes  it  less  compact.  But  its  enlarge- 
ment goes  to  the  account  of  its  height,  and  has  no  influence  on  the  area 


Air  Currents 


FlG.   70. 


occupied  by  it.  The  advantages  afforded  in  return  by  the  zigzag 
appear  in  the  quality  of  the  bolting,  as  the  distance  the  grain  travels  is 
longer,  besides  which  the  product  is  sifted  from  the  head  of  the  sieve, 
whereas  in  the  first  machine  the  passing  stock  falls  on  different  parts 
of  the  next  sieve,  and  does  not  travel  the  whole  length  of  it. 

The  fan  of  this  zigzag  of  Robinson's  makes  600  revolutions,  the 
sieves  520  vibrations  per  minute,  the  capacity  being  60  to  260  bushels 
per  hour. 

Machines  with  an  Inclined  Rotating  Sieve. — With  the  view  of  obvia- 
ting vibration  generated  by  the  reciprocating  motion  of  the  working 
parts,  which  has  a  bad  effect  upon  the  machine  and  the  building, 
engineers  suggested  separators  with  flat  inclined  sieves  gyrating 


82 


FLOUR   MILLING 


[CHAP.  HI 


on  the  principle  already  explained.  The  box  C  (Fig.  71)  contains  four 
sieves,  1,  2,  3,  and  4.  This  box  is  suspended  from  the  frame  on  four 
reed-springs  c  and  connected  in  with  the  driving-pin  of  the  fly  wheel  Q  by 
counterweights.  The  fly-wheel  is  set  on  a  shaft  rotated  by  a  belt  drive. 
The  stock  is  delivered  into  the  feed  hopper  A,  its  flow  being  controlled 
by  a  gate  balanced  either  by  a  spring,  as  shown  in  the  drawing,  or  by  a 
weight.  The  roll  B  feeds  evenly  the  sieve  1,  an  air-current  s  removing 

at  the  same  time  the  light  im- 
purities. Sieve  1,  inclined  to  the 
left,  sifts  off  the  large  refuse  d, 
dropping  the  throughs  on  to  sieve 
2,  which  gives  the  medium  im- 
purities r  as  refuse,  and  sifts  the 
grain  through  to  sieve  3.  The 
tails  of  the  third  sieve  are  the 
large  grain  o,  and  the  throughs 
are  thrown  on  sieve  4,  where  the 
small  grain  o  is  retained,  and  the 
sand,  dust,  and  other  fine  particles 
m  pass  through.  The  grain  o  and 
o1  passes  down  the  air- tube  v,  and 
once  more  undergoes  the  process 
of  separation  from  the  light  im- 
FIG.  71.  purities.  The  heavier  particles 

of  dirt  a  settle  in  boxes  t,  and  are 

taken  out  through  inclined  spouts  fixed  to  the  bolting  box.  The  number 
of  revolutions  of  the  box  is  250,  and  the  capacity  is  160  bushels  per 
hour. 

Machines  of  the  kind  described  are  built  by  the  firms  of  G.  Luther 
(aspirator  "  Triumph  ")  and  others. 


2.  Separation  according  to  Shape 

In  the  process  of  cleansing  of  the  grain  of  foreign  matters  by  sifting, 
we  have  seen  that  their  removal  is  possible  when  they  greatly  differ 
from  the  kernels  in  size.  But  the  sieves  will  not  remove  impurities 
of  another  shape,  yet  of  a  size  that  agrees  with  the  small  dimension 
of  the  stock  cleaned.  To  those  foreign  bodies  pertain  mostly  spherical 
grains,  or  particles  of  grain  (broken  grain)  of  the  product  treated. 
For  instance,  the  seeds  of  cockle,  or  sweet -pea,  their  diameter 


CHAP,  m]  FLOUR   MILLING  83 

coinciding  in  size  with  the  thickness  of  a  grain  of  wheat,  cannot  be 
separated  from  it.  They  cannot,  too,  be  removed  when  the  stock  is 
sorted  according  to  specific  gravity,  only  the  light  impurities  being 
extracted  here.  If  oats  are  mixed  with  wheat,  their  cross-sections 
coinciding,  they  cannot  be  separated  by  sifting. 

All  machinery  by  means  of  which  impurities,  differing  from  the  main 
stock  in  shape,  are  removed,  is  constructed  on  principles  based  on  the 
following  properties  of  these  extraneous  matters  : 

(1)  Spherical  grains  roll  down  an  inclined  plane  or  curving  surface 
with  a  greater  speed,  and  thus  developing  a  greater  kinetic  energy,  leap 
over  obstacles  which  detain  the  oblong  grains. 

(2)  Spherical  grains  roll  off  a  slightly  inclined  plane,  overcoming  the 
friction  of  rolling,  while  the  oblong  grains  remain  immovable  on.  the 
surface. 

(3)  If  we  have  a  curved  surface  or  inclined  plane  with  semi-spherical 
sockets,  and  stock  moving  over  it,  the  spherical  and  broken  seeds,  will 
fall  into  the  sockets,  and  the  main  stock  will  roll  off. 

(i.)  Machines  of  the  First  Principle 

The  Conic  Apparatus. — The  apparatus  based  on  the  first  principle  is 
exceedingly  simple  (Fig.  72).  There  are  two  conic  surfaces  K±  and  K2. 
The  diameter  of  the  base  of  the  lower  reversed 
end  K2  is  greater  than  the  diameter  of  the  base 
of  cone  K lm  The  plane  of  the  base  of  the  bottom 
cone  is  set  higher  than  the  plane  of  the  base  of 
the  upper  one.  The  grain  flows  out  of  the 
spout  a  on  to  the  surface  of  cone  K±.  The 
round  grains  of  cockle,  pea,  &c.,  developing 
a  greater  rolling  velocity,  have  a  larger  kinetic 
energy.  Hitting  the  prominent  circular  surface 

cc1  of  the  cone  Kz  these  grains  leap  over  the 

,       ,  FIG.  72. 

ring  cc1,   while   the   grains    of   wheat   or   rye, 

in  their  descent,  move  slowly,  and  pass  into  the  cone  K2  and  tube  b. 

The  angle  of  the  cones  is  35°,  the  diameters  of  their  bases  about  three 
metres.  The  cones  are  of  polished  timber.  Though  this  appliance  is 
bulky,  its  capacity  is  great.  Open  cones  would  raise  dust,  therefore 
they  may  be  encased,  which  allows  the  feed  to  be  exhausted. 

The  Worm  Trieur. — The  construction  of  the  worm  trieur  depends  on 
the  same  principle  (Fig.  73).  This  apparatus  consists  of  helicoidal  conic 


84 


FLOUR   MILLING 


[CHAP,  ni 


surfaces,  of  which  one,  two,  or  three,  6,  of  a  smaller  diameter,  are  inscribed 
in  respect  of  the  surface  of  the  large  diameter  a.  These  surfaces  are 
encased  in  a  box  K.  This  trieur  operates  in  the  following  manner  :  the 
stock,  generally  cockle,  broken  grain,  vetch,  and  undersized  grain,  passes 

through  the  feeder  s  to  6,  a  worm  of 
smaller  diameter  running  close  to  the 
axle,  to  which  the  helicoidal  surfaces 
are  fixed.  By  reason  of  the  action  of 
gravity,  the  product  descends  with 
an  according  velocity.  The  round 
grains  (cockle,  &c.)  develop  a  greater 
speed,  and  roll  over  the  rim  b  into  the 
larger  worm,  as  shown  by  arrows.  At 
the  base  there  are  exits  for  the  sorted 
product,  c  for  non-round  grain,  and  d 
for  the  round. 

The  machine  is  often  built  with- 
out a  case,  but  it  is  better  encased, 
as  this  appliance  affords  the  possi- 
bility of  aspirating  the  machine 
by  means  of  an  exhaust  tube  fixed 
as  shown  by  the  arrow  e.  For  in- 
specting purposes  the  machine  may 
be  furnished  with  closely  fitting 
doors. 

This  machine  operates  very  effi- 
ciently ;  the  thread  of  the  worm  and 
the  angle  of  the  cone  being  carefully 
calculated,  it  requires  no  motive  power, 
and  it  is  of  an  exceedingly  simple  construction.  The  flights  of  the  worm 
are  made  of  iron  plate.  The  case  is  also  of  iron.  The  capacity  of  a 
machine  with  a  worm  2000  mm.  in  height,  the  larger  worm  a  being  500 
mm.  in  diameter,  is  from  25  to  40  bushels  per  hour. 


FIG.  73. 


(ii.)  Machines  of  the  Second  Principle 

Two  types  of  construction  belong  to  machines  operating  by  a  moving 
inclined  plane  :  the  first  kind  moves  parallel  to  the  direction  of  the 
rolling  grains,  the  second  at  right  angles. 

Fig.  74  exhibits  a  double  machine  of  the  first  type  manufactured  by 


CHAP.    Ill] 


FLOUR    MILLING 


85 


Rober.     On  a  timber  stand  are  placed  a  feed  box  A  for  the  stock,  and  a 

frame  B  with  working  surfaces  Z),  which  are  endless  leather  cloths  rotating 

in  the  direction  pointed  by  arrows  6%  by  means  of  a  belt-pulley  C  and 

guides  r  enclosed  in   the  cloths.     Through   the   feed   box  J,  the  stock 

is  fed  on   to   D  by  the  feed 

rolls  a.    The  round  grains  roll 

down  (arrow  n),   the   grains 

of  wheat,  rye,  &c.,  are  lifted 

up  on  D  and  thrown  off  into 

a  box  F  below.     The  flow  is 

regulated  by  a  gate  b.     The 

incline  of  the  working  surface  ^t>'  r        t*    ~^— ar 

is  adjusted  with  the  aid  of  a  ^^frf^ 

toothed  gearing  E  and  bolts  v,  FIG  ?4 

which  are  screwed  into  nuts 

0 

u,  and  support  the  lower  parts  of  the  frame.  The  lower  guides  f or  D  are 
mounted  on  adjustable  bearings,  which  makes  it  possible  to  adjust  the 
tension  of  the  cloths. 

The  capacity  of  such  a  machine  attains  12  bushels  per  hour,  the  breadth 

of  the  cloths  being  250  mm.,  their 
length  2500  mm.,  and  the  speed  is 
80  revolutions  per  minute. 

Another  type  of  machine  in 
which  the  cloth  travels  in  a  direc- 
tion at  right  angles  to  the  fall  of 
grain  is  shown  in  Fig.  75.  It  is 
likewise  a  machine  of  double  action. 
Receiving  the  grain  from  the 
I  feed  hopper  the  feeding  rolls  strew 
the  stock  on  the  cloths.  The 
round  grains  roll  off  (arrow  s),  and 
the  rest,  remaining  on  the  cloths, 

are  carried  (arrow  n)  to  the  receiving  box. 

As  in  the  preceding  machine,  the  adjustment  of  the  incline  and  tension 
of  the  cloths  is  provided  for. 

The  utmost  capacity  of  this  machine  is  20  bushels  per  hour,  having 
cloths  300  mm.  broad  and  2200  mm.  long  running  at  the  rate  of  50 
revolutions  per  minute. 


FIG.  75. 


86 


FLOUR   MILLING 


[CHAP,  in 


FIG.  76. 


(iii.)  Machines  of  the  Third  Principle 

The  Normal  Trieur  Type. — In  1845  two  Frenchmen,  Vachon  (father 
and  son),  in  Lyons,  invented  a  machine  which  they  named  a  "trieur." 
The  machine  was  a  sheet-iron  cylinder  bossed  on  the  interior  surface 
with  cylindrical  sockets.  Inside  the  cylinder,  set  at  an  incline,  was 
enclosed  a  conveyor  box,  almost  throughout  its  full  length,  at  the  same 

angle  of  inclination.  Into  the  raised 
end  of  the  cylinder  the  grain  was 
poured,  and  when  rotating  the 
round  grains  of  foreign  plants,  fall- 
ing into  the  sockets,  were  lifted  to  a 
sufficient  height  and  then  dropped 
into  the  stationary  conveyor  box. 
The  grain  travelled  down  the 
cylinder  by  gravity,  shaken  also  by 
the  longitudinal  rocking  of  the  cylinder,  while  the  round  particles  of 
impurities  rolled  down  the  inclined  plane  of  the  conveyor  box.  Both 
grain  and  impurities  fell  into  conveyor  boxes  placed  under  the  lower 
end  of  the  cylinder. 

During  the  seventy  years'  existence  of  Vachon's  cleaner  and  separator 
its  working  principle  has  not  undergone  any  modification.  The  modern 
sorting  cylinder  has  but  received  modifications  of  construction,  and  Fig. 
76  gives  us  its  present  plan. 
A  cylinder  G  turns  on  a 
stationary  shaft  v  in  the 
direction  of  the  arrow  s.  The 
mass  of  stock  Q  rolls  along 
the  cut  surface  of  the  cylin- 
der ;  the  round  kernels  of  the 
admixture,  and  the  broken  grain  of  the  stock  to  be  cleaned,  fall  into 
the  sockets,  and  are  lifted  up  and  dropped  into  a  stationary  conveyor 
box  D,  rolling  down  its  sloping  surface  b.  The  impurities  are  pushed 
along  the  conveyor  box  by  a  worm  T  revolving  in  the  opposite 
direction. 

A  full  drawing  of  this  machine  is  to  be  found  in  Fig.  77.  The  shaft 
of  the  cylinder  is  placed  on  props  t-t.  When  the  set  screws  of  the  props 
are  loosened  the  shaft  may  be  turned.  On  the  revolving  hub  of  the 
cylinder  is  set  a  gear  z  coupling  with  the  gear  z1  of  the  worm  conveyor  T 


FIG.  77. 


CHAP,  in] 


FLOUR   MILLING 


87 


of  the  box  which  is  fixed  to  the  shaft.  The  refuse  is  delivered  by  means 
of  the  worm  down  6.  The  taper  imparted  to  the  cylinder  is  usually 
0*08  to  0*1,  i.e.  8-10  mm.  to  100  mm.  of  its  length. 

The  capacity  of  the  trieurs  depends  on  the  circumferential  velocity 
of  the  cylinder.  It  is  obvious  that  their  capacity  increases  with  the 
velocity.  Nevertheless  that  velocity  must  have  a  highest  limit  of  signi- 
fication, otherwise  the  centrifugal  force  of  the  grains  will  press  them  to 
the  surface  of  the  cylinder,  and  they  will  not  fall  into  the  conveyor  box. 

Let  us  examine  the  conditions  which  allow  of  the  most  profitable  work. 
Fig.  78  shows  us  various  positions  of  a  socket  with  a  grain.  If  the  re- 
volving velocity  of  the  cylinder  is  v,  the  grain  develops  a  centrifugal  force 

—  ^  —  ,  r  being  the  radius  of  the  cylinder.     Besides  that  the  grain  is 

under  the  influence  of  its  proper  weight 
p=mg. 

When  the  grain  is  in  a  diametrical 
plane,  position  /,  it  is  evident  that  it  will 
not  fall  out  of  its  socket,  whatever  the 
rotatory  velocity  may  be,  as  the  resultant 
Z=  Vc2Jrp2  will  press  it  into  the  socket. 
When  in  position  //,  the  grain  being 
raised  to  an  angle  a,  the  resultant  is 
(in  the  triangle 


!  v 
-K-T-^-'V 


Sin  a 


FIG.  78. 


Thus,  Z  differentiates  in  accordance  with  the  angle  not  only  in  size 
but  also  in  direction,  which  is  of  great  importance  to  us.  The  angle  X, 
defining  the  direction  of  Z,  is  gradually  widened  to  180°  for  the  third 
position  of  the  grain,  when  a  =  90°.  Let  us  see  when  the  grain  will  begin 
to  drop  out  of  the  socket. 

If  op,  we  have  seen  that  the  grain  remains  in  the  socket.  When 
c=p,  position  III  proves  that  the  grain  is  balanced,  seeing  that 
Z=0(sina  =  l,  Z=V2c2-2c2  =  0).  Therefore  the  dropping  of  the 
grain  is  possible  only  when  c<p,  which  determines  the  revolving  velocity 
of  the  cleaner  and  separator.  We  shall  have  obtained  the  limit  of  signi- 
fication of  the  velocity  of  revolution  when  Z=0. 

Then  c=--p,  or  —=mg,  whence  v=  Vgr.  Theoretically  speaking, 
the  dropping  out  of  the  grain  ought  to  take  place  when  the  difference  in 
p  -c  is  infinitely  small,  but  usually  not  more  than  one-fifth  Vgr  is  taken, 
because  in  greater  velocities  the  falling  of  the  round  grains  into  the 


88 


FLOUR    MILLING 


[CHAP.-  in 


FIG.  79. 


sockets  will  be  under  a  disadvantage  (the  quick  motion  of  the  stock  on 
the  working  surface),  and  besides  that,  we  have  to  take  into  considera- 
tion the  friction  of  the  kernels  in  the  sockets. 

Before  speaking  of  the  capacity  of  trieurs,  we  must  give  our  attention 
to  the  shape  of  the  sockets.  European  technics 
know  only  one  shape  of  sockets,  semi-spheric,  which 
are  made  either  by  bossing  or  by  drilling.  Fig.  79 
shows  drilled  (7)  and  bossed  (77)  sockets  in  operation. 
An  accurate  semi-sphere  cannot  be  obtained  by 
bossing,  therefore  round  grains  will  more  quickly  fall 
out  of  the  bossed  sockets  than  out  of  the  drilled  ones. 
The  receiving  surface  &  of  the  conveyor  box  is  set 
higher  for  7  than  for  77,  and  consequently  the  work- 
ing surface  of  trieur  7,  i.e.  the  area  of  sockets  catching 
the  round  seeds,  is  larger  than  that  of  77.  Besides, 
the  distance  between  the  drilled  sockets  is  less 
than  between  the  bossed  ones,  for  a  close  bossing 
would  have  made,  the  sockets  still  less  regular,  and  damaged  the  material. 
Therefore  a  unit  of  surface  contains  a  greater  number  of  cut  sockets 
than  of  bossed  ones,  which  raises  the  capacity  of  trieurs  7,  in  comparison 
to  trieurs  77,  working  under  the  same  conditions.  The  difference  in  the 

number   of  sockets  to   the  same  area  reaches  25  per          

cent.  For  instance,  a  cockle  cylinder  numbers  29,000 
bossed  sockets  to  one  square  metre  of  surface,  and 
36,500  drilled  sockets  to  the  same  area. 

Fig.  80  shows  us  that  both  kinds  of  sockets  are 
turned  in  the  direction  of  rotation  not  of  their 
spherical,  but  cylindrical  surface.  This  is  to  prevent 
friction  and  the  choking  up  of  the  sockets  with  small 
refuse  when  the  grains  drop  out,  as  shown  in  the  case 
of  the  grain  A  in  77  (Fig.  79). 

Besides  semi-spheric  sockets,  the  Prinz  Manufactur- 
ing Co.  (Milwaukee)  offer  bossed  sockets,  shown  on 
Fig.  81,  the  lower  surface  of  which  is  either  flat,  1,  or 
cylindric,  2.  The  factory  maintains  that  round  impurities  a  will  be 
lifted  higher  and  fall  more  easily  out  of  sockets  of  that  shape. 
That  is  indeed  so,  but  owing  to  their  shape  the  number  of  sockets 
to  $  unit  of  surface  is  small  in  comparison  to  the  number  of 
semi-spheric  sockets,  and  consequently,  the  capacity  of  these  trieurs  is, 
not  large. 


Bossed  fockets 


FIG.  80. 


CHAP.    Ill] 


FLOUR    MILLING 


89 


The  material  of  which  the  trieur  cylinders  are  made  is  zinc  sheets. 
Sometimes  the  socketed  surface  of  the  cylinder  is  bronzed  for  the  sake 
of  durability. 

The  number  of  sockets  to  a  unit  of  surface  in  a  trieur,  speaking  gene- 
rally, depends  on  its  purpose.  Besides  removing  round  grains,  a  trieur 
may  serve  as  a  barley  or  oat  separator. 
To  this  end  larger  sockets  and  a 
smaller  incline  of  the  cylinder  are 
adopted.  In  this  case  the  wheat  and 
rye  fall  into  the  feeder,  while  barley 
and  oats,  being  larger,  roll  off  the 
cylinder. 

The  Capacity  of  Trieurs  of  the  Normal 
Type. — The  capacity  of  the  trieurs  de- 
pends on  the  length,  the  diameter  of 
the  cylinder,  and  the  circumferential 
speed  of  its  rotation  (see  the  table 
below). 

The  barley  and  oat  separators,  being 
trieurs  for  larger  grains,  are  larger  in  diameter.  The  incline,  35 
to  40  mm.  to  1  m.  of  length  of  the  cylinder,  is  less,  as  a  longer 
period  in  the  cylinder  is  needed  for  high-class  work. 


FIG.  81. 


TABLE  XI 


CAPACITIES  OF  COCKLE  CYLINDERS 


Dimensions  of  Cylinder. 

Approximate  Capacity  per  Hour. 

Number 

of  Revolutions 

Diameter, 
mm. 

Length, 
mm. 

per  Minute. 

Wheat  and  Eye, 
Bushels. 

Controlling  or 
Re-  Trieuis, 
Bushels. 

Oats, 
Bushels. 

300 

1120 

21J-16 

7-5 

4-3 

4-3 

350 

1250 

20-15 

10-7 

5-4 

7-5 

400 

1500 

18-14 

17-14 

8-6 

10-8 

450 

1750 

17-13 

24-20 

12-10 

14-12 

500 

2000 

15-12 

32-26 

16-12 

18-16 

550 

2250 

14-11 

,  40-32 

20-16 

24-13 

600 

2500             13-10 

50-40 

24-40 

28-24 

700 

2750    *. 

11J-9 

75-45 

38-26 

36-31 

800 

3000 

10-8 

100-65 

50-32 

44-38 

90 


FLOUR   MILLING 


[CHAP,  in 


TABLE  XII 

CAPACITIES  OF  TRIEURS  FOR  SEPARATING  BARLEY 
AND  OATS  FROM  WHEAT  AND  RYE 


Dimensions  of  Cylinder. 

Number 
of  Revolutions 
per  Minute. 

Approximate 
Capacity 
per  Hour, 
Bushels. 

Diameter, 
mm. 

Length, 
mm. 

350 

1250 

22 

4 

400 

1500 

20 

6 

450 

1750 

19 

10 

500 

2000 

17 

13 

550 

2250 

15 

16 

600 

2500 

14 

20 

700 

2750 

13 

26 

800 

3000 

11 

33 

Trieurs  of  other  Construction. — Making  a  theoretical  estimation  of 
the  capacity  of  trieurs  of  the  normal  type,  it  is  easy  to  note  that  the 
defect  of  this  machine  is  the  impossibility  of  utilising  its  full  working 
surface,  owing  to  the  very  nature  of  the  construction.  The  working  sur- 
face is  used  only  from  A  to  B  (Fig.  76) ;  this  constitutes  30  to  33  per  cent, 
of  the  whole  cylindric  surface,  as  has  been  proved  by  practical  tests.  Here 
we  meet,  in  fact,  the  same  constructive  principle  that  is  applied  in  the 
round  and  hexagon  separating-reels.  But  the  problem  of  the  most  efficient 
bolting  machine  was  brilliantly  solved  by  the  invention  of  the  plan- 
sifter,  in  which  almost  the  whole  working  surface  is  utilised,  whereas  the 
normal  type  of  trieur  has  not  yet  been  supplanted  by  a  more  perfect 
machine. 

The  trieur  with  an  inclined  table  "  Record  "  patented  by  Heinrich 
Seek  adopts  the  idea  of  an  inclined  plane.  The  working  surface  of  this 
machine  (Fig.  82)  consists  of  an  endless  cloth  15,  with  trieur  sockets. 
The  cloth  is  combined  of  separate  narrow  plates  connected  by  joints, 
and,  embracing  the  drums  A- A ,  is  set  at  an  incline.  The  grain  is  delivered 
into  the  feeder  1,  and  falls  on  the  band  which  travels  upwards.  The  flow 
of  grain  is  regulated  by  hand  with  the  gate  3,  by  means  of  a  handwheel  2, 
and  a  gear  drive.  The  round  bodies  dropping  into  the  sockets  are  carried 
away  by  the  band,  and,  at  the  curve  of  the  band  on  the  drum,  fall  into 
hopper  4,  while  the  grain  rolls  down  the  inclined  surface  of  the  band 
into  hopper  5. 


CHAP.    Ill] 


FLOUR   MILLING 


91 


Besides  rotating,  the  cloth  makes  about  250  transversal  vibrations  per 
minute,  and  the  motion  is  shafted  in  the  following  manner.  The  drum 
bearings  are  placed  on  iron  cross-head  and  shippers  14,  which  in  their 
turn  are  mounted  on  flexible  stands  12  and  13 ;  when  the  driving  shaft  8 
rotates,  the  eccentric  drive  18  reverses  the  motion  of  the  cloth.  From 
the  shaft  8,  by  means  of  a  belt,  worm  16,  and  chain-gearing  16,  the  rota- 


FIG.  82. 

tory  motion  is  imparted  to  the  upper  driving  drum  which  moves  the  cloth. 
Being  no  innovation  in  its  constructive  idea,  this  machine  possesses 
all  the  defects  of  machines  with  reciprocative  motion,  and  besides,  its 
construction  is  exceedingly  complicated  in  comparison  with  the  tneur 
of  the  normal  type,  yet  it  affords  no  larger  working  surface  than  the 
common  trieur.  The  possibility  of  revising  its  design  is  of  no  value,  as 
the  machine  cannot  be  aspirated.  The  absence  of  means  of  regularly 
lubricating  the  link  joints  of  the  band,  must  lead  to  their  speedy 
wear. 


92 


FLOUR    MILLING 


[CHAP,  in 


IV 

MACHINES  FOR  SEPARATING  STONES 

The  mass  of  grain  often  contains  stones  of  such  shapes  and  sizes  that 
they  can  be  removed  neither  by  means  of  aspirators  nor  of  trieurs.  In 
such  cases  the  aid  of  machinery,  the  working  idea  of  which  is  based  on 
the  utilisation  of  gravity,  has  to  be  invoked. 

Hignett's  Stone  Separator. — Hignett's  machine  consists  of  a  triangular 
wooden  box  (Fig.  83)  with  a  low  rim,  inclined 
towards  the  vertex  of  the  triangle.  On  the 
bottom  of  the  box  are  placed  triangular  boxes  of 
smaller  size,  with  rims  nm.  The  first  box  a 
serves  as  feeder  for  the  stock  to  be  cleaned, 
which  passes  out  of  it  in  the  direction  pointed 
by  arrows,  there  being  no  front  partition  to  a. 
Another  box  D,  with  higher  rims,  is  placed  at 
the  top  c  of  the  box.  This  box  collects  the 
stones  owing  to  the  absence  of  a  part  of  the  rim 
in  the  point  c  encased  on  the  box  D.  In  the 
rim  at  the  back  AB  of  the  box,  there  are  holes 
00,  through  which  the  grain  is  discharged. 
This  box  is  mounted  on  flexible  rods  F.  By 
the  body  of  the  connecting  rod  T  of  a  crank 
mechanism,  a  vibration  is  communicated  to  the 
box  (90  to  120  revolutions),  owing  to  which 
the  grain  leaving  a  is  hit  by  the  sides  mn. 
These  blows  throw  the  grain  in  the  direction 
of  the  discharge  openings  00,  while  the 

stones,  being  heavier,  roll  down  the  inclined  plane  influenced  by  their 
own  gravity.  Of  course,  the  incline,  the  oscillation,  and  the  number  of 
reciprocations  of  the  box,  must  be  so  calculated  that  the  gravity  of 
the  stones  (its  component  on  the  plane  of  the  bottom  of  the  box)  is 
greater  than  the  resultant  of  their  friction  against  the  wood  of  the  box, 
and  greater  than  the  inertia  from  the  oscillations.  When  suitably  inclined 
and  vibrating,  the  same  machine  may  be  used  for  separating  the  light 
kernels  from  the  heavy  ones. 

G.  Luther's  Machine. — Luther's  machine  (Fig.  84),  constructed  on 
the  same  principles  as  that  of  Hignett,  is  more  perfect.  A  box  A  is  set 


FIG.  83. 


CHAP.    Ill] 


FLOUR   MILLING 


on  sixteen  flexible  props.  The  inclination  of  the  stone-separating  box  e 
with  triangular  rimmed  boxes  s  as  in  Hignett's  machine  is  adjustable, 
being  adjusted  with  the  aid  of  screw  rods  and  hand-wheels  d  fixed  to 
the  frame  of  the  box .  On  the 
box,  down  its  full  length,  is 
set  a  conveyor  box  (7,  with 
discharge  openings  1,  2,  3,  4 
into  box  e.  By  means  of  a 
crank  mechanism,  the  ma- 
chine is  oscillated  (up  to  120 
revolutions ) .  The  stock  flows 
into  the  feeder  C,  and  tra- 
velling as  shown  by  the  arrow 
passes  into  the  machine  through  openings  1,  2,  3,  4.  The  grain  is  carried 
upwards,  and  is  delivered  through  spout  a,  while  the  stones  roll  down  the 
inclined  plane  and  pass  out  through  spout  6. 

The  capacity  of  the  machine  is  70  to  100  bushels  per  hour. 


FIG.  84. 


SCOURING  AND  POLISHING  THE  GRAIN 
1 .  Principles  of  the  Processes  and  the  Character  of  the  Working  Parts 

After  the  removal  of  foreign  matter  from  the  grain,  it  has  to  be 
cleaned  of  the  dirt  that  has  stuck  to  it,  and  the  husk,  smut,  and  beard. 
The  dirt  is  sometimes  noticed  here  and  there  on  the  surface  of  the  grains, 
but  generally  it  lies  in  its  groove.  As  to  the  husks,  which  encase  the 
grain  in  a  compact  armour,  they  must  be  removed,  because  they  contain 
no  nutritive  substances  for  the  human  organism,  and  then,  triturated 
together  with  endosperm,  they  impart  a  darker  colour  to  the  flour,  and 
reduce  its  properties  in  every  respect. 

The  modern  processes  of  removing  the  dirt  and  husks  may  be  divided 
into  two  categories  :  (1)  the  dry  process  of  scouring,  and  (2)  the  wet 
process,  when  the  dirt  is  washed  off  previously. 

In  the  first  instance,  the  working  parts  of  the  machinery  either  by 
friction  or  by  striking,  oftenest  both  by  strokes  and  friction  of  rough 
surfaces,  remove  the  dirt,  shells,  germ  coat,  and  beard,  or  hairs  covering 
the  grain  (oats).  The  second  process  consists  in  a  preliminary  removal  of 
a  part  of  the  dirt  by  washing,  and  then  both  the  husk  and  the  remaining 
dirt  are  removed  by  dry  scouring.  From  the  structure  of  the  berry 


94  FLOUR   MILLING  [CHAP,  in 

we  have  learned  that  the  first  three  shells  grow  very  closely  together. 
The  outer  skins  are  comparatively  less  firmly  attached  to  the 
seed-shells,  but  the  latter  are  so  solidly  welded  to  each  other  and 
to  the  endosperm,  that  their  removal,  without  partiaUy  injuring  the 
endosperm,  is  an  impossibility,  even  by  chemical  means.  For  this 
reason  the  effect  of  the  working  parts  on  the  grain  must  not  be  so 
powerful  as  to  destroy  the  grain,  for  the  particles  of  grain  broken  off 
together  with  the  shell  in  the  process  of. cleaning  are  irretrievably  lost 
to  the  flour.  Consequently,  in  modern  flour  milling  technics,  the  so- 
called  "  washing  of  the  grain,"  originally  designed  to  remove  the  dirt 
off  the  grain,  plays  a  prominent  part.  But  an  explanation  of  its  real 
aim  will  be  found  below. 

The  dry  as  well  as  the  wet  processes  of  cleaning  have  the  removal  from 


FIG.  85. 

the  berry  of  the  "  beeswing,"  and  the  dirt  covering  it,  in  view.  As  the 
washing  process  requires  mechanical  treatment  of  the  grain  for  removing 
the  beeswing  as  well,  the  machines  employed  for  that  purpose  must  be 
examined  first. 

The  scouring  of  grain  is  best  carried  out  by  means  of  rough  surfaces, 
having,  as  it  were,  microscopic  knives  which  shave  the  outer  stem 
off,  or  rough  metal  surfaces.  Therefore  the  working  organs  of  the 
machine  must  be  : 

(1)  Sharp  and  rough    surfaces,  such   as  stones  of  natural  and  arti- 
ficial origin. 

(2)  Surfaces  of  thick   wire-cloth   of  round  or  square  section   (Fig. 
85). 

(3)  Perforated  iron   or   steel  plates   with   a  grating  surface,  which 
operate  with  the  edges  of  the  torn  metal  in  the  place  of  knives  (Fig.  86). 

(4)  Ingot  cast-iron  or  steel  surfaces  with  cutting  facets. 


CHAP.    Ill] 


FLOUR   MILLING 


95 


The  Shape  and  Motion  of  the  Working  Surfaces. — In  every  machine, 
be  it  a  motor-engine,  or  an  operating  machine,  if  its  construction 
will  allow,  reciprocal  motion  should  be  avoided.  This  is  particularly 
important  as  regards  operating  machinery  in  which  a  constant 
speed  of  the  working  organs  is  necessary  for  a  uniform  effect  upon  the 
product.  This  is  indispensable  to  the  uniformity  of  the  quality  of 
the  work. 

Consequently,  from  the  general  fact  of  transmission  of  work, 
it  must  be  admitted  that  an  even  motion  of  the  working  surfaces 
is  absolutely  necessary,  as  the  greatest  efficiency  is  yielded  by  such 
work. 

Taking  this  into  consideration,  engineers  should  ignore  the  reciproca- 
ting motions  (rectilinear,  or  tangential)  where  either  an  empty  run  of 


FIG.  86. 


the  working  organ  or  variable  speeds  of  motion  are  observed. 
But,  as  a  steady  motion  can  be  attained  best  by  a  gyratory  one,  it 
is  evident  that  the  working  parts  of  the  machinery  must  be  a  rotating 
surface  :  (1)  of  a  terminal  radius  (cylinder,  cone,  globe,  &c.),  (2)  of  an 
endless  radius  (plane). 

In  selecting  the  face  of  the  working  surface,  a  steady  speed  at  all 
points  of  its  motion  has  to  guide  the  choice.  In  that  case  the  effect  of 
the  working  organs  upon  the  product  will  be  uniform  at  all  points  of 
contact,  keeping  up  a  steady  productivity  to  a  unit  of  surface,  and  an 
even  wear  of  the  working  surface.  That  condition  of  uniform  treatment 
of  the  product  and  economy  of  machine-work,  precludes  the  use  of  conic, 
hyperbolic,  and  suchlike  working  surfaces,  and  leaves  us  only  the  cylinder. 
The  simplicity  of  construction,  and  the  cheapness  of  such  machines, 
both  of  which  demand  consideration  in  practice,  speak  for  the  expediency 
of  adopting  the  terminal  surface,  i.e.  the  plane,  in  machinery. 


FLOUR   MILLING 


[CHAP,  in 


Thus  the  shape  of  working  surfaces  decided  upon  as  the  most  efficient 
is  the  rotating  surface,  and  its  motion  a  steady  gyration. 

Let  us  examine  the  shape  of  the  working  organs  of  machines 
accepted  in  practice.  They  have  cylindric,  conic,  and  flat  faces.  In 
respect  to  the  position  of  the  axis  of  rotation  of  the  working  organs,  the 
machines  may  be  divided  into  those  with  a  horizontal  axis,  and  machines 
with  a  vertical  axis  of  rotation..  The  treatment  in  regard  to  stock 
requiring  two  working  organs,  two  states  in  regard  to  the  degree  of 
activity  of  each  are  possible  :  (1)  one  of  the  working  organs  is  in  motion, 
and  the  other  one  is  stationary  ;  (2)  both  organs  are  in  motion. 

Cylindrical  Surfaces  of  Rotation. — The  machines  with  cylindrical  work- 
ing surfaces  can  be  divided  into 
two  groups :  with  a  vertical,  and 
with  a  horizontal  axis  of  rotation. 
We  shall  examine  the  first  group 
(Fig.  87). 

As  regards  the  motion  of  the 
working  surfaces,  three  combinations 
are  possible  :  ( 1 )  only  the  outer  cylin- 
der A  rotates,  (2)  only  the  inner 
cylinder  B  rotates,  (3)  both  cylinders 
revolve  in  opposite  directions. 

In  the  first  case  (Fig.  87,  /),  the 
stock  fed  in  the  direction  of  arrow  r 
can  be  treated  only  if  the  distance 
between  the  working  surfaces  is  less 
than  the  largest  measurement  of  the  grain.  A  grain  of  corn  a  pressed 
by  the  surface  A  travels  in  between  the  surfaces  A  and  .B  in  a  helical 
curve  (it  would  represent  a  parabola  on  a  plane),  influenced  by  its  proper 
gravity  (mg)  and  by  friction.  But  the  grain  is  liable  to  be  crushed  by  the 
pressure.  Therefore  the  first  combination  must  be  rejected. 

In  the  second  case  (Fig.  87,  //),  the  cylinder  A  being  stationary  and 
B  rotating  in  the  direction  s,  the  distance  between  A  and  B  may  be 
greater  than  the  length  of  the  grain.  Falling  on  the  surface  B  the  grain 
receives  a  percussion,  and  rebounds  to  A  ;  being  thrown  back  by  A,  it  is 
again  thrown  on  to  B,  &c.  Its  route  on  the  plan  is  marked  c,  d,  e  .  .  . 
(Fig.  87,  II). 

In  the  third  case,  i.e.  when  A  and  B  rotate  in  opposite  directions,  the 
grain,  rebounding  from  B,  would  be  thrown  against  A  by  centrifugal 
force.  It  will  be  enabled  to  travel  downwards,  if  the  velocity  of  rotation 


FIG.  87. 


CHAP,  in]  .  FLOUR   MILLING  97 

of  A  is  so  small  that  the  friction  generated  by  the  centrifugal  force  of  A 
is  less  than  the  gravity  of  the   grain,   i.e.  f^-<mg,  where  /  is  the 

coefficient  of  friction  of  the  grain  and  the  surface  A,  r  the  radius  of  A, 
m  the   mass  of  the  grain,   and  g  acceleration  of  the  gravity.      This 

defines   v</yy.     Though  the  calculation  of  such  a  velocity  is  possible, 

by  making  cylinder  A   of  a  corresponding  radius,  the  building  of  the 
machine  will  be  complicated. 

In  addition,  in  regard  to  the  character  of  the  motion  given  to  the 
grain,  this  type  of  machinery  approaches  the  second  combination  and, 
therefore,  it  would  be  purposeless  to  complicate  the  machine  by  adopting 
two  moving  surfaces. 

Of  the  combined  motions  of  A  and  B,  just  reviewed,  general  practice 
has  adopted  only  the  second  form.  g  eL  A 

Fig.  88  represents  two  cylindrical 

surfaces  A  and  B,  having  horizontal     JU_      _i  _  1  _   J \ I 

axes  of  rotation.      As  in  the  case  of       \i  \  \     /          \    \ 

vertical  cylinders,  we  shall  give  our 
attention  to  the  rotation  of  but  one 
cylinder  B,  for  the  rotation  of  the 

outer  cylinder  imparts  a  centrifugal  power  to  the  grain,  which  presses  it  to 
the  surface,  but  there  is  nothing  to  impel  it  out  by  way  of  arrow  r.  It 
would  be  possible  to  treat  the  grain  between  two  moving  cylinders,  but 
the  complexity  of  the  machinery  -makes  it  inadvisable  in  practice.  The 
only  remaining  combination  is  that  of  one  stationary  cylinder  A  and  one 
rotating  B.  The  cylinder  B  must  be  furnished  with  helical  blades  to 
give  the  grain  a  travelling  motion.  The  route  of  the  grain  will  be  a,  6, 
c,  d,  e,  after  the  manner  of  the  thread  of  a  screw. 

Thus  we  shall  occupy  our  attention  with  two  types  of  machines 
having  cylindrical  working  surfaces,  which  answer  their  purpose.  Both 
machines  have  an  outer  stationary  cylinder  A,  and  an  inner  rotating  one. 
Comparing  the  two  styles,  the  advantage  of  the  first  one  (accepted  by 
engineers  in  America)  must  be  acknowledged,  as  the  work  is  evenly 
distributed  over  the  whole  inner  surface  of  A,  whilst  in  machines  with  a 
horizontal  axis  the  lower  part  of  A,  where  the  bulk  of  grain  collects,  is 
used  more  than  the  upper  side,  which  brings  about  an  uneven  wear  of 
the  working  surface.  But  as  regards  the  simplicity  of  construction  and 
an  easy  access  for  inspection,  machines  with  horizontal  rotation  are  pre- 
ferable. 


FLOUR   MILLING 


[CHAP,  in 


Conic  Gyrating  Surfaces.  —  Fig.  89  presents  the  same  combinations  of 
conic  surfaces  and  their  motions  as  those  of  the.  cylinders  ;  the  sole  differ- 
ence lies  in  there  being  two  combinations  for  the  vertical  axis,  with  the 
cone  pointing  upwards  and  downwards.  The  considerations  mentioned 
respecting  the  combinations  of  motion  of  the  surface,  and  of  the  product 
in  the  cylinders,  may  be  repeated  here.  But  the  defect  of  machines  with 
conic  surfaces  in  general,  is  the  variability  of  their  circumferential  velo- 
cities of  motion,  and  consequently,  an  uneven  wear  of  these  machines. 
Besides,  if  for  /  we  adopt  a  speed  of  the  rotating  cone  B  at  its  top  D 

sufficient  to  rub  the  husk  off  or 
take  the  germ  and  beard  away, 
at  base  E  that  speed  will  be 
greater  and  might  destroy  the 
grain.  If  vice  versa,  the  upper 
part  of  the  casing  will  not 
work. 

Of  all  combinations  of  conic 
surfaces,  practice  has  adopted 

X  JL  I  and  ///,  in  which  only  the 

inner  cones  gyrate.  Yet,  we 
must  admit  that  a  very  grave 

defect  in  these  machines,  viz.  the 

\ 

variable  speeds  of  the  gyrating 
working  organ,  makes  the  ma- 
chines with  cylindrical  surfaces 
preferable  in  practice. 

In  combined  machinery  we 
often  meet  conic  surfaces  pointing  downwards.  It  is  interesting  there- 
fore to  find  out  when  the  motion  of  the  stock  is  possible.  We 
shall  follow  the  movements  of  the  cone  A,  while  the  cone  B  remains 
stationary. 

The  grain  a,  lying  on  the  inner  side  of  the  cone  at  the  point  a,  has  a 

centrifugal  force  l  c  —  —  —  ,  where  m  is  the  mass  of  the  grain,  v  the  velocity 

of  gyration  of  the  cone  at  a,  a  a  half  of  the  angle  of  the  cone.  Besides 
that,  the  grain  lies  under  the  influence  of  its  own  weight  mg.  To 
allow  the  grain  to  travel  downwards,  the  force  P  must  exceed  the  sum 
total  of  the  power  of  friction  and  S,  i.e.  : 


See  p.  87. 


CHAP,  in]  tfLOUR   MILLING  99 

where  /  is  the  coefficient  of  friction  of  the  grain  upon  A.  After  due  sub- 
stitutions, transferring  8  into  the  left-hand  side  of  the  equation,  we 
have  : 

P  —  S  >f  ( cos  a +mg  sin  a 


or 


wiv*  r  /mvi 

mgcos  a-—  --  sin  a>f(  —  cos  a-j-ragr  sin  a), 

and  we  define  the  significance  of  v  supplanting  f=tg  <p  : 

v  <Vgr  cos  tg 


It  is  clear  now  that  since  the  angle  of  the  cone  is  given,  the  largest  corre- 
sponding r  has  to  be  chosen. 

Movement  of  the  grain  upwards  is  possible,  if  v  <\/gr  cos  tg  (a  +  y). 
Here  also  a  value  must  be  chosen  which  would  satisfy  the  inequality. 

Flat  Surfaces.— As  in  the  two 
preceding  cases,  here  (Fig.  90) 
we  also  have  a  vertical  and  a  hori- 
zontal axis  of  rotation,  or  the 
working  surfaces  /  and  //.  For 
I  we  shall  suppose  the  upper 
surface  alone  revolving.  The  stock 
fed  into  the  space  between  the 
working  surfaces,  to  be  impelled 

to  its  exit  requires  pressure  which  generates  a  centrifugal  power. 
But  that  pressure  results  in  the  breaking  down  of  the  grain,  and,  there- 
fore, such  a  combination  may  be  adapted  only  for  millstones.  If  B  is  in 
motion,  the  grain  falling  on  it  develops  a  centrifugal  force  without  the 
aid  of  pressure.  Consequently,  this  combination  is  more  suitable.  The 
rotation  of  both  A  and  B  presents  an  acceptable  combination,  though 
complicated  in  construction. 

A  horizontal  axis  of  rotation  for  A  or  B  separately,  or  both  together, 
will  effect  the  treatment  of  grain,  if  the  space  between  them  is  less  than 
the  largest  measurement  of  the  grain.  Therefore  the  breaking  down  o 
the  grain  is  unavoidable  here.  Besides  that,  the  stationary  surface  will 
wear  unevenly.  For  example,  B  being  stationary,  the  sectoral  hatched' 
part  OCD,  i.e.  the  part  receiving  the  fresh  supply  of  grain,  will  be  the 
most  worn. 

We  shall  now  pass  to  the  description  of  machines  used  in  modern 
flour-milling  practice. 


100  FLOUR   MILLING  [CHAP,  in 

2.  Construction  of  Scouring  Machines 
(i.)  Machines  with  a  Vertical  Axis  of  Rotation 

It  was  mentioned  above  that  scouring  machines  with  a  vertical  axis 
are  being  almost  exclusively  constructed  in  America.  Some  ten  years 
ago  the  European  factories  imitated  the  American  ones,  but  at  present 
scarcely  one  of  the  large  factories  in  Europe  builds  vertically  rotating 
scouring  machines.  The  reason  for  this  lies  in  the  difficulty  of  finding  the 


FIG.  91. 


FIG.  92. 


equilibrium  of  the  gyrating  drum,  and  the  heavy  load  on  the  step- 
bearing  of  the  drum  which  carries  the  whole  weight.  The  lighter 
machinery  with  a  vertical  axis  of  rotation,  however — brush  machines, 
for  instance — are  also  built  by  European  factories. 

A  typical  American  scourer  employed  for  removing  the  germ  coat 
and  beard,  as  well  as  scouring  the  shells,  is  Prinz's  machine  in  Milwaukee. 
Fig.  91  gives  a  general  view  of  the  machine,  the  casing  being  removed, 
Fig.  92  a  longitudinal  section,  Fig.  93  a  section  down  Zi-Z,  the  step- 
bearing,  details  of  the  wire-cloth,  working  casing,  and  a  detail  of  a  beater 
of  another  construction,  with  a  casing  of  bossed  iron  plate. 


CHAP.    Ill] 


FLOUR 


101 


The  machine  is  mounted  on  a  solid  cast-iron  foundation,  with  a 
bolted  cross-head  for  the  step-bearing.  The  perforated  or  wire  casing 
is  stationary  ;  to  it  are  attached  conic  plates  Y  forming  five  floors.  The 
revolving  shaft  carries  six  discs  with  beaters  Uv  The  upper  disc  is 
solid,  the  nether  one  is  perforated  to  give  access  to  the  outer  air.  Each 
disc,  the  top  one  as  well,  is  covered  with  a  cylindrical  sieve,  to  keep  the 
grain  from  rolling  down  the  plate  to  the  shaft.  The  work  is  performed 
in  the  following  manner  :  the  grain  falls  through  the  spout  Kl  on  the 
disc  W,  and  is  thrown  by  centrifugal  force  to  the  drum.  Here  it  is  caught 
up  by  the  beaters  and  whipped  against  the  wire  several  times,  till  it  falls 
on  to  the  first  plate  and  rolls  down  to 
the  second  scouring  disc,  &c.  On 
reaching  the  last  scouring  disc,  the  grain 
passes  its  last  stage  of  treatment, 
and  is  then  delivered  through  the 
spout  Bv 

The  spout  B1  has  a  valve  Dt 
which  automatically  regulates  the  dis- 
charge of  finished  stock.  The  grain 
flows  through  the  tube  (7l5  which  sup- 
plies the  fan  with  air,  carrying  the 
heavy  extraneous  matter  away  with  it. 
The  heavier  refuse  settles  on  the  sides 
of  the  leg  F1?  while  the  lighter  par- 
ticles pass  through  the  fan,  either  to 
the  dust  collector  or  into  the  dust 
chamber. 

The  machine  is  aspirated  in  the 
following  manner  :  the  arrows  T-T  mark  the  influx  of  the  air.  Stream- 
ing in  through  the  holes  in  the  casings  in  a  direction  opposite  to  the  flow 
of  the  grain,  it  drives  the  loose  husks,  dust,  beeswing,  beards,  and  other 
light  matter  out  through  the  fan. 

The  space  between  the  wire  caging  and  the  beaters  is  greater  at  the 
top  and  less  below,  owing  to  which  the  grain  undergoes  a  gradually 
increasing  scouring,  and  is  treated  with  most  energy  on  the  last  floor,  before 
leaving  the  machine.  On  Fig.  93  we  see  that  the  scouring  blades 
37  are  bolted  to  the  discs,  which  allows  them  to  be  replaced  when  worn. 

"  Eureka  "  of  Schneider,  Jacquet  &  Co.— This  (Fig.  94)  is  one  of  the 
combined  type  of  machines.  One  shaft  v  carries  a  fan  F,  beaters  C,  and 
brushes  D,  The  stationary  working  drum  H  is  made  of  perforated 


FIG.  93. 


^  •» 


102 


FLOUR    MILLING 


[CHAP,  in 


wire  and  covered  with  an  iron  casing.  The  grain  flows  down  A  and 
is  thrown  against  the  drum,  where  it  is  energetically  dealt  with  by  iron 
beaters.  Then,  down  the  conic  plate  of  the  upper  stationary  brush,  the 
stock  rolls  on  to  the  revolving  brush,  and  thrown  by  centrifugal  force  into 
the  space  between  the  grass  or  wire-brushes,  is  freed  of  the  partly-cut 
skins,  and  of  that  part  of  the  dirt  still  adhering  to  it  after  the  scouring, 
and  lastly  flows  down  the  spout  B  through  tube  F,  where  it  is  aspirated. 
The  heavy  refuse  is  discharged  by  spout  6r,the  medium  through  the  valve  K, 
and  the  light  matter  passes  out  through  the  fan.  The  air  current  running 
through  the  machine  is  marked  by  arrows  pointing  upwards.  The  dis- 


FIG.  94. 


tance  between  the  brushes  is  regulated  by  raising  the  step-bearing  with 
the  aid  of  a  hand- wheel  m  that  lifts  by  a  screw  the  cross-head  t,  upon 
which  the  step-bearing  rests.  The  whole  machine  is  mounted  on  two 
hollow  cast-iron  columns,  and  driven  by  a  belt  pulley  8  which  may  be 
placed  either  at  the  top  or  below.  The  number  of  revolutions  is  400 
to  500  ;  its  capacity,  according  to  the  size  of  the  machine,  is  20  to  30 
bushels  per  hour. 

A  Brush  Machine  from  the  Works  of  form.  Seek  Bros.  (Fig.  95),  with 
conic  working  surfaces  of  grass  brushes,  is  designed  for  the  final  removal  of 
abraded  bran  not  quite  separated  by  the  scouring  machines,  dust  collected 
in  the  crease  of  the  grain,  and  the  semi-separated  germ  envelopes.  The 
grain  flowing  along  spout  A,  on  to  the  conic  surface  of  the  stationary  upper 
brush  B,  falls  on  the  disc  of  the  revolving  brush,  and  is  thrown  by  centrifugal 


CHAP.    Ill] 


FLOUR    MILLING 


103 


force  into  the  working  space  between  the  brushes.  On  leaving  the  first 
pair  of  brushes  the  stock  passes  to  the  second  pair,  &c.,  until  it  reaches 
the  bottom,  where  it  is  conveyed  by  scrapers  revolving  conjointly  with 
the  brushes  to  the  discharge  spout,  and  there  undergoes  a  final  aspiration. 


The  stationary  brush-drum  is  perforated.  With  the  aid  of  an  air  current, 
the  scoured  shells,  germ  membranes,  &c.  are  impelled  through  the  per- 
forations of  the  casing  into  C,  the  ring  space  between  the  drum  and 
the  casing.  The  lighter  refuse  is  carried  away  through  the  fan,  the 
heavier  particles  return  to  the  grain,  and  are  finally  removed  by  a  more 
powerful  draught  of  fresh  air  at  its  exit  through  the  discharge  spout. 


104 


FLOUR   MILLING 


[CHAP,  in 

The  factory  produces  these  machines  in  seven  sizes,  and  the  following 
table  shows  their  capacity : 

TABLE    XIII 

CAPACITY  OF  BRUSH  MACHINES 


No. 

Number  of 
Floors. 

Number  of 
revolutions  per 
Minute. 

Horse-power 
Required. 

Approximate 
Capacity  per 
Hour, 
Bushels. 

0                    1 

500 

1 

12-20 

00 

2 

500 

14 

24-36 

000           3 

500 

2 

40-50 

1 

1 

500 

11 

20-32 

2 

2 

500 

2 

40-60 

3 

3 

450 

3 

75-80 

4 

4 

450 

4 

100-120 

The  space  between  the  brushes  is  regulated,  as  in  the  preceding 
machine,  with  the  aid  of  a  supporting  cross-head,  which  may  be  raised 
and  lowered  by  means  of  rods  carrying  hand-wheels  on  their  upper 
screw  ends. 

Before  ending  our  review  of  the  scouring  machines  with  a  vertical 
axis  of  revolution,  it  must  be  noted  that  all  attempts  on  the  part  of 
constructors  to  build  a  machine  with  two  revolving  surfaces  failed,  for 
the  result  was  either  a  very  complicated  construction  or  the  treatment 
sustained  by  the  grain  was  too  severe.  The  grain  was  not  only 
scoured,  but  broken  down  at  the  same  time. 


(ii.)  Machines  with  a  Horizontal  Axis  of  Rotation 

The  most  convenient  shape  for  working  surfaces  in  machinery  with  a 
horizontal  axis  of  rotation  is  the  cylinder,  though  conic  and  flat  surfaces 
are  also  employed  in  practice.  In  all  machines  with  cylindric,  conic,  or 
flat  surfaces,  generally  but  one  of  them  is  in  motion,  this  being  the  in- 
terior surface  in  the  first  two  types. 

In  describing  the  operation  of  a  machine  with  horizontal  surfaces  of 
rotation,  it  must  be  pointed  out  that  only  under  the  most  favourable 
circumstances  is  the  whole  of  the  stock  caught  up  by  the  inner  surface 
and  travels  in  a  helical  line  over  the  working  space.  The  outer  stationary 
surface  is  usually  whole,  while  the  rotating  interior  one  is  built  of  separate 
parts  in  the  shape  of  beaters  or  brushes,  set  in  a  helical  line,  to  drive  the 
stock  through  the  machine  to  its  exit, 


CHAP.   Ill] 


FLOUR    MILLING 


105 


The  stationary  working  surface  of  these  machines  is  generally  made 
of  metal  (perforated  metals  or  wire  cloth),  or  of  artificial  stone  (mostly 
of  emery,  carborundum,  &c.).  The  rotating  surface  is  made  of  steel 
beaters,  artificial  stone,  and  metal  or  fibre  brushes. 

In  calculating  or  verifying  the  capacity  of  cylindrical  machines,  one 
may  be  guided  by  the  following  considerations  : 

Suppose  we  have  a  scouring  machine  of  the  normal  type,  with  an 
emery  or  perforated  metal  casing,  on  which  the  grain  is  thrown  and 
treated  by  beaters.  The  beaters  are  arranged  aslant,  in  respect  to  the 
generating  circle  of  the  casing  ;  owing  to  that  inclination,  the  grain 
moves  over  the  surface  of  the  casing  and  describes  a  helical  line  the 


f. 

x 

r 


1     F  A     |\    ^    /I     IT 


rrV^VA-f^ib 


V       1       V       V       V 


Sb 


FIG.  96. 


length  of  which  depends  on  the  magnitude  of  the  angle  a  at  which  the 
beaters  are  inclined  (Fig.  96). 

The  longer  that  helical  trajectory  of  the  grain  is,  and  the  thinner  the  layer 
of  grain  moving  along  that  trajectory,  the  better  will  the  stock  be  cleaned. 

The  degree  of  inclination  x  of  the  beater  will  be  expressed  in  depend- 
ence of  the  size  of  the  casing  thus  : 

X  =  Ltga. 

The  pitch  of  the  helical  trajectory  of  the  grain  is  : 


The  number  of  threads  in  the  screw  of  the  trajectory  is 

7    L-    ^ 

£J  =-T~  —      ~~T\~~' 

h     nDx 
The  length  of  the  helical  trajectory  of  the  grain  is  : 


A 

A= 2  = 

COS  a          X  COS  a 


x 


whence 


*  =  -; 


106 


FLOUR    MILLING 


[CHAP,  in 


For  the  wheat  to  be  satisfactorily  cleaned  after  a  triple  scouring,  the 
trajectory  of  the  grain  A  has  to  be  1400  inches  long.1  The  value  of  A 
being  so  great  in  comparison  with  the  length  of  the  casing  L,  the  latter 
may  be  ignored  under  the  radical  ;  the  inclination  of  the  beaters  then  is 

X     ^ 
=  1- 

If  over  1  inch  of  the  pitch  of  the  helical  trajectory  of  the  grain  B  bush. 
of  grain  will  be  passing  per  hour,  the  capacity  of  the  scouring  machine 
may  be  expressed  as 


If  the  length  of  A  is  1400  inches,  as  defined  above,  B  must  be  reckoned 


DUST 


at  20  to  24  bush,  per  hour  (the  length  of  D  and  L  is  reckoned  in  inches). 

This  formula  coincides  almost  perfectly  with  the  practical  data 
obtained  by  personal  observation  of  the  operation  of  horizontal  emery 
scouring  machines  in  Russian  and  foreign  factories. 

Let  us  now  pass  to  the  constructive  description  of  these  machines. 

The  emery  scouring  machine  of  the  factory  form.  Seek  Bros.  (Fig.  97) 
may  be  regarded  as  the  normal  type  of  machine  of  this  kind. 

In  a  stationary  emery  casing  a  there  rotates  at  a  speed  of  350  to 
700  revolutions  per  minute  (varying  with  the  size  of  the  machine),  a  drum 
furnished  with  beaters  6,  which  fling  the  grain  fed  (Einlauf)  into  the 
casing  against  its  sides,  where  the  shells  are  cut  open  and  torn  off  by  the 
sharp  edges  of  the  emery. 

*  The  circumferential  velocity  of  the  beaters  employed  was  1 5  nit,  per  sec.,  their  direction  radial. 


CHAP.    Ill] 


FLOUR    MILLING 


107 


When  thrown  with  great  force  and  severely  scoured,  the  grain  is  freed 
of  the  germ  membrane  and  beard  as  well.  The  separated  light  husks  are 
sucked  up  by  the  exhaust  c,  while  the  germ  membrane  and  heavier 
shells  fall  into  the  conveyor  e  and  are  carried  out. 

With  a  view  to  keeping  the  operating  chamber  of  the  machine  com- 
municated with  the  fan  for  ventilating  purposes,  a  part  of  the  wall  of  the 
emery  casing  is  removed,  and  in  its  stead  is  placed  an  iron  sliding  section 
d  with  sifting  meshes.  This  section  is  so  arranged  as  to  exclude  the 
possibility  of  any  bran-dust  settling  on  it.  In  passing  through  the 
automatic  discharge  valves  at  the  exit  of  the  machine,  the  grain  is  once 
more  thoroughly  exhausted. 

For  the  operation  to  be  always  accurate,  the  emery  casing  must  be 
suitably  fitted.  In  the  first  place,  the  material  must  be  very  porous, 
otherwise  the  working  surface  soon  becomes  dirtied,  but,  at  the  same 
time,  the  emery  must  be  very  hard  to  stand  the  wear.  A  complete 
obviation  of  wear  of  the  emery  surface,  however,  being  impossible,  the 
beaters  may  gradually,  in  proportion  to  its  wear,  be  set  nearer  to  the 
working  surface,  thus  keeping  them  and  the  surface  at  a  normal  distance 
from  each  other. 

This  machine  is  used  for  cleaning  wheat  and  rye.  Its  construction 
is  very  simple,  it  allows  of  easy  access  to  all  its  parts,  and  the  working 
parts,  if  damaged,  can  without  difficulty  be  replaced  by  new  ones. 

The  scouring  drum  and  the  fan  are  mounted  either  on  ball-bearings 
or  bearings  with  ring  lubrication,  according  to  the  speed. 

The  frame  and  the  outer  parts  of  the  machine  are  either  of  timber  or 
iron  (the  first  four  numbers)  for  fire-proof  mills.  The  size  of  the  casing 
and  the  capacity  of  the  machines  are  mentioned  below. 

TABLE    XIV 

CAPACITY  OF  HORIZONTAL  EMERY  SCOURING  MACHINES 


Dimensions  of  the  Emery  Casing. 

Number  of 

Approximate  Capacity  per  Hour. 

No. 

Diameter, 
mm. 

Length, 
mm. 

of  the  Drum 
per  Minute. 

Rye,  Ibs. 

Wheat,  Ibs. 

1 

820 

1500 

350 

4000-4800 

6100-7000 

2 

720 

1500 

400 

3000-3600 

4500-5200 

3 

720 

1250 

400 

2100-2700            2700-3600 

4 

620 

1100 

450 

1600-2000 

2100-2700 

5 

520 

1000 

550 

900-1300 

1600-2000 

6 

420 

900 

650 

540-720 

900-1300 

7 

370 

800 

700 

430-540                650-900 

1 

108 


FLOUR   MILLING 


[CHAP,  in 


The  Scourer  by  Dobroff  <$o  Nabholtz.  —To  the  same  type  of  machinery 
belongs  the  emery  scourer  constructed  of  iron  by  the  Dobroff  & 
Nabholtz  factory  in  Moscow.  In  this  machine  the  time  the  grain 
takes  to  pass  through  it  may  be  regulated. 

In  Fig.  98  we  see  that  the  scourer  consists  of  a  rotating  drum 
containing  iron  beaters  a,  a  leather  casing  6,  and  a  fan  c.  The  beaters 


/ 


FIG.  98. 

in  the  drum  have  a  less  angle  of  inclination  here  than  in  scourers  of  the 
normal  type. 

The  appliance  adapted  to  regulate  the  time  of  passage  through  the 
machine  consists  of  the  following  :  Opposite  the  sieve  covering  the 
opening  of  the  emery  casing  on  the  inside  there  are  arranged  valves  ii, 
forming  a- Venetian  blind.  These  valves  are  connected  by  a  common  rod, 
ending  on  the  outside  in  g  with  a  screw-thread  and  a  hand- wheel  h.  The 
Venetian  blind  conveys  the  stock  in  a  helical  line  defined  by  the  angle  of 
the  inclination.  By  means  of  the  hand- wheel  h  and  the  rod  g  a  greater 
or  smaller  inclination  may  be  imparted  to  the  valves,  in  accordance  with 
which  the  grain  will  pass  faster  or  slower  through  the  working  chamber. 


CHAP.   Ill 


FLOUR   MILLING 


109 


owing  to  the  influence  the  Venetian  blind  (patent  of  the  factory)  has  in 
this  case  upon  the  pitch  of  the  helical  route  of  the  grain. 

The  shaft  of  the  drum  rotates  on  ball-bearings  (Fig.  99).  As  re- 
gards other  details,  in  its  main  outlines  the  machine  does  not  differ  from 
the  normal  type  of  scourer. 

T.  Robinson's  Emery  Scourer. — The  greater  part  of  English  and 
American  factories  have  developed  their  own  type  of  scouring  machinery, 


FIG.  99. 

different  from  the  European  normal  type  of  construction,  the  fan 
and  the  scouring  drum  being  set  on  one  and  the  same  axis,  while  the  con- 
veyor which  carries  the  heavy  refuse  away  has  been  supplanted  by  a 
hopper  from  whence  the  screenings  pass  out  by  themselves.  Besides 
that,  the  machine  is  enclosed  in  a  chamber  which  ends  in  a  box  for  heavy 
refuse  at  the  bottom. 

Fig.  100  represents  a  scouring  machine  of  Thos.  Robinson's  works, 
at  Rochdale  (England).  In  the  stationary  casing  K  covered  with  emery- 
mass  on  the  inside,  there  rotates  a  scouring  drum  D.  On  the  same  shaft 


110  FLOUR   MILLING  [CHAP,  m 

v  as  the  drum  is  set  a  fan  A.  The  drum  is  enclosed  in  a  chamber 
ending  in  a  hopper  B  below.  The  machine  operates  in  the  following 
manner  :  The  stock  is  delivered  into  the  feeder  provided  with  a  balanced 
valve,  and  passes  through  the  aspirator  leg  s  to  the  hopper  b,  which  con- 
veys the  grain  into  the  machine.  While  passing  through  the  tube  s,  the 
stock  is  subjected  to  the  first  aspiration,  and  freed  of  the  light  matter. 
In  the  emery  casing  the  grain  is  separated  from  germ  covering,  beard, 
and  shells,  almost  all  of  which  pass  through  the  sieve  d  down  the  whole 
length  of  the  casing,  because  through  the  meshes  the  casing  is  played  on 
by  a  strong  exhaust.  The  light  particles,  passing  through  d,  are  sucked 
up  through  the  spout  Q  to  the  fan,  leaving  the  less  light  matters  on 
their  way  in  the  refuse  box  r,  while  the  heavier  impurities  fall  down  into 
the  hopper  B.  The  cleansed  grain  flows  to  its  exit  down  c,  and  is  for 


FIG.  100. 

the  third  time  aspirated  here  by  a  contrary  air-current  c,  which  carries 
away  all  the  light  matter  remaining  after  the  bolting  on  d.  Thus,  the  air 
is  conveyed  to  the  fan  from  the  casing  chamber  and  by  the  two  spouts, 
T  and  T \,  where  the  grain  is  purified  at  its  ingress  and  egress. 

The  fact  that  this  machine  has  a  common  shaft  for  the  fan 
and  the  scouring  drum,  and  the  absence  of  a  conveyor,  simplify  its 
construction  to  a  large  extent,  and  reduce  the  expenditure  of  power  for 
driving  the  fan  and  the  conveyor.  But  a  common  shaft  compels  both 
the  fan  and  the  scouring  drum  to  perform  the  same  number  of  revolu- 
tions. However,  if  the  expenditure  of  air  be  correctly  calculated,  an 
equal  rotation  may  be  assigned  to  the  drum  and  the  fan,  and  conse- 
quently, this  circumstance  cannot  be  viewed  as  a  defect. 

The  drum  of  the  machine  rotates  with  the  velocity  of  350  to  480 
revolutions  per  minute,  and  the  capacity  is  40  to  280  bushels  per  hour, 
according  to  the  size  of  the  machine. 


CHAP.   Ill] 


FLOUR   MILLING 


111 


An  Emery  Scouring  Machine  with  an  Elliptic  Casing. — An  interesting 
scouring  machine  in  its  idea  is  described  by  Fr.  Kettenbach.1  It  is  to  be 
regretted,  though,  that  he  mentions  neither  the  works  where  it  is  built 
nor  the  patent  (Fig.  101). 

The  scouring  drum   of  this  machine  is   like  the  normal  type  one, 
but  the  upper  part  of  the  emery  sleeve  is  of  an  elliptic  shape  in  section, 
while  the  lower  end  which  is  of  the  usual  form  is  clothed  with  a  sieve 
for  bolting  the  beeswing,  the  broken  grain,  and  heavy  screenings.     Down 
the  full  length  of  the  casing  there 
stretches  a  plank  A ,  which  may  be 
turned  by  means  of  a  lever  on  its 
axis  0.     This  plank  carries  paddles 
d   which,    like    a   Venetian  blind, 
may  be  turned  by  a  common  rod 
protruding    outwards    beside    the 
lower  fastenings.     The  grain  pass- 
ing   into    the    scouring    machine 
through  the  feed  C  is  caught  up  by 
the  beaters  and  thrown  upon  the 
curved  emery  surface  of  the  casing 
E,  over  which  the  author  supposes 
it  to  slide.      In  its  sliding  path  the 
outer  bran  coats-  are  rubbed  off. 
On  reaching  a  certain  height,  and 
having  expended  its  power  of  in- 
ertia, the  grain  falls  on  the  plank  A , 
down  which  it  rolls  into  the  crevice 
between  the  casing  and  the  plank. 
Owing  to  the  adjustability  of  the 
plank  A  round  its  axle  0,  the  size  of  crevice  may  be  altered.      If  the 
Venetian  blind  d  be  inclined  to  the  side  reverse  to  the  movement  of  the 
grain  in  the  casing,  the  grain  rolls  down  to  that  part  of  the  beaters  which 
receive  it   at    the   bottom   of  the  casing.     The  blind   may  be  so  in- 
clined that  the  path  of  the  grain  will  be  in  a  zigzag  line,  i.e.  the  beaters 
will  be  impelling  more  grain  than  will  return  along  the  plant.     That  will 
prolong  the  time  of  treatment  of  the  grain.     The  grain  undergoes  a  triple 
aspiration  by  fan  F,  when  fed  in  by  an  air-current  in  the  spout  T,  in  the 
machine,  through  the  sifting  part  of  casing  S  (the  air  is  conveyed  into 
the  machine  through  72),and  lastly,  on  its  exit  through  s  into  the  spout  T2, 

1  Der  Mutter  und  der  Miihlenbauer,  pp.  143-144.     Leipzig,  1907. 


FIG.  101. 


FLOUR    MILLING 


[CHAP,  m 


by  a  draught  in  slt  impelled  by  the  fan  up  2\.  The  heavier  particles  of 
refuse  passing  through  S,  fall  into  hopper  D,  the  less  heavy  ones  settle 
in  the  dust  air-chamber  G,  while  the  light  matter  is  carried  out  through 
the  fan. 

This  machine  is  interesting  in  its  conception,  but,  firstly,  it  is  compli- 
cated in  construction,  secondly,  the  path  of  the  grain  will  not  be  sliding, 
as  the  author  maintains,  but  will  run  in  a  broken  line  1-2-3-4-5, 
for  the  angle  of  incidence  of  the  grain  generates  an  identical  angle  of 
reflection.  Consequently,  the  grain  will  be  scoured  through  its  succes- 
sive percussions  against  the  emery  surface  of  the  casing. 

Brush  Machine. — Fig.  102  represents  a  horizontal  brush  machine, 
the  essential  points  in  the  construction  of  which  are  as  follows. 
The  arrow  a  marks  the  path  of  the  grain  into  the  chamber  A  of  the 

machine.  Passing  through  the 
feeder,  it  is  exposed  to  a  draught 
r  induced  by  the  fan  F.  which 
removes  light  impurities.  The 
chamber  A  is  a  rectangular  box 
with  a  semi-cylindric  bottom 
formed  by  the  surface  of  a  bolting- 
cover  B.  The  rotating  drum  D 
carries  a  brush  arranged  in  a 
spiral.  In  cleansing  the  grain  of 

the  dust  secreted  in  its  creases,  and  abraded  bran,  the  brush  drives  the 
product  to  the  exit  a3,  where  it  encounters  the  air-current  r1  which 
carries  the  light  refuse  remaining  after  bolting  on  B  into  the  worm 
box  E.  The  throughs  of  the  sieve  B  are  taken  by  the  worm  to  the 
discharge  spout  and  delivered  through  a.  The  shafting  is  sufficiently 
outlined  in  the  drawing.  Sometimes  a  belt  drive  takes  the  place  of 
the  gear  drive  k-k^  between  the  brush  and  the  worm. 

This  machine,  with  slight  alterations,  is  built  by  almost  all  European 
works. 

The  brush-drum  runs  at  the  rate  of  75  to  90  revolutions  per  minute, 
the  fan  500  to  600.  The  capacity  of  the  machine  is  10  to  50  bushels  per 
hour,  varying  with  the  size  of  the  machine. 


FIG.  102. 


(iii.)  Combination  Scouring  Machines 

In   cases   where   the   process    of   grain- cleaning   must  be   shortened 
out  of    considerations  of    economy,  separate  bolting  or  brush  machines 


CHAP.   HlJ 


FLOUR   MILLING 


113 


for  the  final  freeing  of  grain  of  the  shells  are  not  installed,  but  combined 
machinery  is  generally  brought  into  use.  Such  machinery  is  mostly 
designed  for  small  mills. 

Wolfs  Combination  Machine.— Fig.  103  shows  an  American  machine 
from  '  The  Wolf  Co."  works  in  Chambersburg.  It  is  a  combination 
of  the  scouring  and  brush  machines.  The  product  is  fed  on  a 
longitudinally  rocking  tray  A,  where  large  and  small  impurities  are 
separated  from  it.  Then  it  runs  down  s  into  the  scouring  drum,  meeting 
a  current  of  air  s1  on  its  way,  which  carries  off  the  dust  and  light  refuse, 
and  is  then  conducted  through  tube  t  to  the  fan  F  (the  full  length  of  the 
tube  t  is  not  shown  in  the  sec- 
tional drawing).  The  scouring 
part  of  the  machine  consists  of  a 
perforated  metal  casing  B  and  a 
drum  (7,  the  latter  being  a  shaft 
on  which  several  corundum  (kind  of 
emery)  discs  are  set  aslant.  When 
the  drum  is  rotating,  the  discs 
compel  the  grain  to  move  to  and 
fro  over  the  lower  part  of  the 
casing,  the  backward  movement 
being  shorter  than  the  forward. 
Travelling  to  the  exit  k  in  this 
way,  the  grain  is  scoured.  The 
spout  L  takes  it  to  the  brush 
machine  D,  from  whence,  follow- 
ing arrow  szt  it  passes  to  the 
outlet,  encountering  an  air  current  s3,  which  removes  the  light  particles 
that  had  not  passed  through  the  perforated  casing  delivering  them  to 
the  hopper  E. 

Both  the  corundum  scouring  and  the  brush  machine  are  so  aspirated 
as  to  subject  the  stock  undergoing  treatment  to  a  triple  exhaust, 
viz.  when  fed  to  the  machine,  in  the  working  chamber,  and  at  its 
delivery ;  while  in  addition,  if  we  take  into  consideration  the  fanning 
the  grain  receives  in  passing  out  of  the  corundum  scouring  part  to  the 
brush  machine,  we  may  reckon  the  aspiration  to  be  quintuple. 

G.  J.  Zolotuchin's  "Record." — This  machine  represents  the  combina- 
tion of  a  zigzag  separator  and  a  scourer,  and  pertains,  therefore,  to  the 
class  of  machines  serving  for  decorticating  the  grain. 

It  works  in   the  following   manner.     The  grain,   when   fed  into   a 

H 


FIG.  103. 


114 


FLOUR   MILLING 


[CHAP,  ill 

(Fig.  104),  before  falling  on  the  first  sieve  of  the  separator  B,  passes 
through  a  current  of  air  induced  by  the  fan  C. 

The  light  matters,  such  as  dust,  chaff,  husks,  and  shrivelled  grain, 
differing  from  the  sound  grain  in  their  specific  gravity,  are  carried  out 
through  the  spout  b  to  the  chamber  A.  In  that  chamber,  as  outlined 
in  dots,  there  are  arranged  a  system  of  partitions  and  a  valve  n  to 


FIG.  104. 

regulate,  as  required,  the  draught  which  carries  the  lightest  particles 
through  the  delivery  spout  /;  the  heavier  particles  collect  in  the 
chamber  A. 

The  impurities  settling  in  the  mouth  of  the  chamber  A  overcome  by 
their  weight  the  pressure  of  the  outer  air  upon  the  valves  et  and  ez,  and 
opening  them  automatically,  fall  out.  In  this  way,  free  of  all  light 
foreign  particles  and  dust,  the  grain  falls  out  of  the  feeder  on  to  the 
sieve  of  the  zigzag  separator. 

On  sieve  1  are  eliminated  the  largest  impurities,  such  as  straws,  lumps 


CHAP,  m]  FLOUR   MILLING  115 

of  earth,  &c.,  which  roll  down  a  sheet  5  into  the  sleeve  6.  The  grain, 
passing  through,  falls  on  the  sieve  2,  where,  again,  impurities  larger  than 
the  grain  are  sifted  off,  while  the  grain  falls  through  on  a  sheet-iron 
bottom  8,  which  transfers  the  mass  of  grain  to  the  sieve  3. 

The  meshes  of  the  sieve  3,  also,  bolt  the  grain  and  tail  over  matters 
of  somewhat  larger  size.  The  grain  bolted  on  sieve  3,  totally  free  of  all 
impurities  exceeding  it  in  size,  is  transmitted  by  a  sheet-iron  tray  9  to 
the  last  sieve  4. 

The  meshes  on  sieve  4  are  smaller  in  diameter  than  the  cross  section 
of  the  grain,  thus  retaining  it  on  the  surface. 

Consequently,  on  this  sieve  all  the  smaller  impurities  are  separated  from 
the  grain,  and  falling  on  a  sheet-iron  tray  10,  pass  off  into  spout  7, 
while  the  grain,  perfectly  cleansed  of  large  and  small  matter,  rolls  off  the 
sieve  4  into  the  spout  Z  and  is  conveyed  to  the  receiver  Z±  of  the  scouring 
drum,  the  construction  of  which  is  shown  separately.  The  grain  falling 
on  the  drum  is  caught  up  by  rapidly  revolving  beaters,  and  the  brushes  dl 
fling  it  on  the  inner  surface  of  a  casing  made  of  woven  steel  cloth, 
or  of  emery. 

The  rapidly  rotating  brushes  polish  the  grain  and  remove  the  dust 
settled  in  the  crease.  In  this  manner  the  grain  is  scoured  in  the  drum, 
polished  with  a  brush,  and  passes  through  the  spout  N  to  the  spout  m. 
In  passing  out,  the  mass  of  grain  is  again  aspirated  as  it  flows  through  the 
spout  N,  which  is  connected  with  the  dust  air  chamber  F  and  the  fan  (7. 

The  dust  chamber  F  is  arranged  similarly  to  the  chamber  A,  i.e.  it 
is  furnished  with  partitions  and  a  valve  n. 

(iv.)  Scouring  Machines  with  Flat  Working  Surfaces 

Koloonock. — One  of  the  first  machines  designed  for  the  removal  of  germ 
coverings,  beard  and  husk  from  the  grain,  was  the  millstone  "  koloonock," 
still  in  use  in  some  old  mills  (Fig.  105).  It  consists  of  an  upper 
revolving  stone  A  and  a  fixed  lower  one  B.  The  distance  between  the 
two  stones  does  not  exceed  the  average  thickness  of  the  grains  under 
treatment,  and  is  adjusted  by  means  of  a  crank  worm  gearing  C  driven 
by  a  hand- wheel  D.  The  stock  is  fed,  as  shown  by  arrow  s,  to  the  hopper, 
passing  through  a  magnet  apparatus  a.  On  leaving  the  working  space 
of  the  millstones,  it  is  bran.  The  loosened  exhausted  husks,  &c.,  are  carried 
away  by  a  draught  in  the  direction  pointed  by  arrow  Sj  and  caught  up 
again  by  a  fresh  air-current  s2  at  the  bottom  of  the  spout  e.  In  the  expan- 
sion chamber  E  a  series  of  partitions  is  arranged,  owing  to  which  the 


116 


FLOUR   MILLING 


[CHAP,  ill 


swirling  air  currents  develop  a  centrifugal  force  which  throws  the 
heavier  particles  into  the  spout  /,  where  they  slide  down  to  the  outlet. 
The  less  heavy  matter  falls  into  the  spout  c,  while  the  lightest  particles 
are  sent  to  the  fan  through  d. 

This  machine  is  rather  bulky,  and  the  inadjustability  of  the  distance 
once  established  between  the  stones,  blocks  the  passage  for  grains  of  a 
larger  size,  thus  producing  a  large  percentage  of  broken  grain.  The 
natural  result  of  this  has  been  its  dropping  out  of  use. 

An -Emery  Scourer  by  the  Mechanical  Engineer,  V.  A.  Moskaleff.— 
MoskalefT's  machine,  with  vertical  grindstones,  is  designed  to  adjust 
the  distance  between  the  surfaces  automatically.  Consequently,  the 

aim  of  this  device  is  to  set 
aside  the  defect  of  the  millstone, 
i.e.  the  breakage  of  grain  (Fig. 
106). 

On  a  horizontal  shaft  1  there  is 
set  a  metal  disc  2  enclosed  in  a 
casing  3  of  the  same  material,  and 
rotated  by  a  belt-pulley  4.  To 
the  front  annular  part  of  the  disc 
an  emery  washer  5  is  fixed  by 
bolts,  the  heads  of  which  are  sunk 
into  the  washer.  A  similar 
washer  6,  but  composed  of  two 
halves,  is  attached  to  the  bottom 
of  the  casing.  The  grain  is  fed 

into  the  machine  by  pouring  it  through  the  hopper  7  into  the  funnel  8, 
which  covers  the  middle  concave  part  of  the  disc,  shaped  to  suit  the  form 
of  the  basin  9. 

The  funnel  8  is  adjustable  and  set  on  three  bolts,  the  heads  of  which  rest 
on  the  flexible  plates  attached  to  the  funnel,  and  by  which  it  is  pressed 
against  the  disc.  The  grain  poured  into  the  funnel  is  thrown  by  centrifugal 
force  to  its  edges  in  an  even  layer.  A  sufficient  quantity  of  stock  in 
the  basin  9,  being  given  a  centrifugal  motion,  presses  back  the  rim  of 
the  funnel,  and  the  grain  is  evenly  distributed  in  a  fan  shape,  through 
the  annular  aperture  now  open,  into  the  working  space  between  the 
emery  washers.  In  this  manner  the  funnel  plays  the  part  of  an  appliance 
for  the  equable  feeding  of  the  working  surfaces. 

The  pressure  of  the  grain  against  the  rotating  washer  5  is  transmitted  by 
a  spring  through  the  footstep-bearing  to  the  stop  10  with  hand- wheel  11. 


FIG.  105. 


CHAP.    Ill] 


FLOUK    MILLING 


117 


118  FLOUR   MILLING  [CHAP,  m 

This  spring  is  the  tension-brake  of  the  washer  5.  The  spring  must 
be  so  calculated  as  to  contract  when  the  washer  is  pressed  by  grains 
of  larger  size,  and  then  the  distance  between  the  washers  increases,  and 
the  grain  leaves  the  working  space  unbroken. 

The  action  of  the  hand- wheel  11  controls  the  degree  of  pressure  of 
the  washer  5,  and  the  distance  between  the  washers.  At  the  other  end 
of  the  shaft  1  there  is  a  guard  bolt  12  which  defines  the  least  distance 
between  the  washers.  The  finished  grain  passes  through  the  spout  13  in 
the  lower  part  of  the  casing  and  through  the  trunk  14,  where  a  draught 
of  air  aspirated  by  the  fan  15  carries  the  husks  and  beeswing  away.  The 
air  laden  with  light  impurities  is  driven  out  of  the  fan  to  the  expansion 
chamber  16,  where  it  deposits  the  less  light  matter  in  the  hopper  17, 
while  the  lighter  refuse  passes  through  the  discharge  opening  18,  and  is 
carried  out  through  the  tube  19.  The  air  draught  is  controlled  by  a 
lid  20,  which  is  opened  more  or  less,  as  occasion  demands. 

For  the  balancing  of  the  disc  2  on  its  reverse,  there  is  a  slide  21  along 
which  two  iron  plates  are  shifted,  and  may  be  fixed  in  any  particular  spot. 

The  idea  of  this  machine  is  undoubtedly  correct,  and  we  shall  return 
to  it  again,  when  speaking  of  millstone  sets  with  vertical  working  surfaces. 


3.  Special  Machinery 

Grain  Cleaning  with  Bran. — In  the  scouring  process  of  grain  cleaning, 
the  germ  covers,  husks,  and  beard  are  supposed  to  be  removed  as  well  as  the 
mud  sticking  to  the  berries.  Generally,  after  a  series  of  machines  sepa- 
rating away  all  extraneous  matter,  the  stock  is  treated  on  the  "  impure  " 
scourer  with  the  view  of  removing  the  dirt  together  with  the  germ  covers 
and  a  part  of  the  husks.  For  this  reason  Haggenmacher's  new  machine 
must  be  referred  to  that  type  of  machinery  which  cleans  the  outer  skin 
of  the  grain.  It  is  well  known  that  almond  bran  is  used  for  cleaning 
furs.  Fine  rye  and  wheat  bran  is  often  made  use  of  too  for  cleaning 
delicate  leathers  (chamois,  &c.).  The  sharp  edges  of  bran  seem  to  work 
like  chisels  in  scraping  the  thin  coating  of  dirt  off  the  surface  of  the 
object.  Evidently,  these  considerations  led  Haggenmacher  to  his  idea 
of  "  washing  "  the  grain  with  bran. 

The  machine  for  cleaning  the  grain  with  bran  (Fig.  107)  consists 
of  an  iron  drum  A,  710x310  mm.  in  dimensions,  mounted  on  two 
U-shaped  iron  beams.  On  four  bearings  B  and  C,  resting  on  the 
same  iron  beams,  there  are  two  shafts  rotating  in  opposite  direc- 
tions one  with  the  velocity  of  100  revolutions,  the  other  of  120  revolu- 


CHAP,  in] 


FLOUR    MILLING 


119 


120  FLOUR   MILLING  [CHAP,  m 

tions  per  minute.  The  ends  of  these  shafts  let  into  the  drum  A  carry  two 
journals  D-D  with  pins  E.  In  the  upper  part  of  the  drum  there  is  an 
outlet  200x200  mm.  in  size,  covered  with  a  valve  F  which  is  pressed 
against  the  drum  by  two  weights  G  set  on  levers,  on  either  side  of  the  valve. 

The  grain  mixed  with  bran  on  passing  out  of  the  drum  through  the 
outlet  flows  into  the  exhaust  trunk  L.  The  air  is  sucked  into  that  trunk 
through  an  aperture  M,  covered  with  a  net.  The  grain  and  bran  are  fed 
to  the  machine  through  the  funnel  Q  and  then  through  two  spouts  N-N. 
In  the  lower  part  of  the  drum  A  there  is  an  outlet  covered  with  a  gate- 
valve,  for  the  discharge  of  its  contents  at  the  end  of  the  operation. 

When  the  journals  D-D  are  brought  into  motion  in  the  mass  of  stock 
filling  the  drum  A,  the  bran  comes  into  close  contact  with  the  grain 
moving  from  the  axis  to  the  periphery  of  the  drum  and  rubs  the  dust 
off  the  outer  covers  and  out  of  the  creases  of  the  grain. 

The  bran  used  in  grain  cleaning  is  fine,  and  the  amount  required  for 
that  purpose  is  10  per  cent,  of  the  stock  in  treatment.  Proportionally 
to  the  accumulation  of  the  grain  and  bran,  the  pressure  in  the  drum 
grows,  until  a  moment  arrives,  when  valve  F  is  lifted,  and  part  of  the 
mixture  is  ejected  out  of  the  drum  into  the  aspirated  trunk  L.  From 
this  trunk  the  grain  passes  into  a  whizzer  for  separating  the  bran. 

A  machine  with  a  drum  of  the  above-mentioned  dimensions  is  sup- 
posed to  clean  1300  bushels  of  grain  per  day  (twenty-four  hours). 

4.  The  Wet  Scouring  and  Washing  Process 

It  has  been  explained  already  that  the  so-called  grain  washing  is  to 
be  regarded  as  one  of  the  processes  of  scouring.  To  distinguish  it  from 
scouring  proper  and  the  bran  washing  method  of  cleaning,  it  may  be 
named  the  "  wet-scouring  process."  This  scouring  process  is  applied  only 
to  wheat. 

When  Amandus  Kahl's  washer  appeared  in  Hamburg  some  twenty 
years  ago — it  appeared  earlier  still  in  England — the  inventor  certainly 
intended  it  to  wash  off  the  dirt.  But  even  then,  in  addition  to  these 
machines,  a  whizzer  was  used  for  drying  and  shelling  the  grain.  The 
grain  was  carried  to  the  whizzer  out  of  the  water-tanks  by  the  same 
water  it  was  washed  in,  and  energetically  stirred  with  the  paddles  of  the 
rotating  drum. 

However,  contrary  to  the  primary  idea  of  washing  the  dirt  off  the 
grain,  practical  experience  in  grain  washing  has  led  the  engineers  to  a  type 
of  washing  process  which  by  its  nature  is  a  wet-scouring  process. 


CHAP,  m]  FLOUR   MILLING  121 

According  to  our  observation,  the  wet-scouring  process  consists 
of  the  following  :  The  grain  is  immersed  in  water  for  a  short  time 
(30  to  40  seconds).  Then  the  excess  of  water  covering  the  grain  is 
removed  by  whizzing.  During  this  interval,  owing  to  the  compara- 
tively great  hygroscopic  properties  of  the  bran,  the  skins  absorb  a  fairly 
even  amount  of  moisture,  and  swell.  Then  the  grain  is  dried.  In 
drying,  the  moisture  in  the  outer  skins  evaporates  faster,  and  they  have 
a  tendency  to  contract,  whereas  the  seed-shells,  still  containing  part  of 
the  absorbed  moisture,  resist  contraction.  This  causes  an  inner  tension 
in  the  outer  skins,  and  they  burst.  This  fact  is  analogous  to  the  burst- 
ing of  a  hoop  on  a  dry  barrel  on  its  being  filled  with  water  and  swelling, 
or  the  radial  bursting  of  wood  when  quickly  dried. 

On  taking  a  berry  after  it  has  been  dried  and  rubbing  it  gently 
between  the  palms  of  the  hands,  we  find  that  it  is  easily  shelled.  When 
inspected  under  a  microscope,  the  shells  prove  to  be  the  berry-husks. 

Grain  washing  in  mills  probably  first  appeared  in  England,  which 
used  to  receive  and  still  receives  grain  from  all  parts  of  the  world. 
Besides  being  polluted  naturally  in  the  places  of  production,  the 
conditions  of  transport  often  contributed  their  share  of  impurities  to  the 
grain.  For  instance,  in  the  eighties  of  the  last  century,  England 
imported  wheat  from  Russian  ports  on  the  Black  Sea  in  coal  holds 
of  ships  that  had  imported  coal  into  Russia. 

It  is  evident  that  much  labour  fell  to  the  lot  of  English  engineers  in 
inventing  washing  machinery  before  the  problem  was  brilliantly  solved. 

A  modern  plant  for  scouring  the  grain  by  washing  has  to  perform 
three  operations  successively,  viz. : 

(1)  Damping  the  grain  copiously. 

(2)  Mechanical  removal  of  water  from  off  the  grain. 

(3)  Drying  the  grain. 

In  examining  the  process  of  scouring  by  washing,  we  shall  inspect  the 
machines  and  apparatuses  pertaining  to  it  in  the  order  they  follow  in 
the  process. 

Th.  Robinson's  Washing  Process.  (1)  Damping  the  Grain.— In  the 
damping  of  grain  Th.  Robinson's  works  take  into  consideration  the  soft 
and  hard  wheats.  We  shall  begin  by  examining  the  appliance  for  damping 
the  soft  wheat.  Fig.  108  is  a  sketch  of  such  a  plant,  the  main  parts  of 
which  are  the  two  tanks  Nos.  1  and  2,  and  a  worm  conveyor  B.  The  tank 
No.  2  is  arranged  in  the  following  manner.  The  upper  cylindrical  part  ends 
in  a  cone  at  the  bottom  provided  with  a  discharge  cock  0.  The  cylinder  is 
provided  with  an  inclined  lid  K,  and  has  a  drain  spout  L  leading  to  tank 


122 


FLOUK   MILLING 


[CHAP,  in 

No.  1.     Into  that  lid  is  set  a  cylinder  7  open  at  the  top  and  at  the  bottom, 
connected  with  the  casing  H  by  means  of  guides  Tc  shaped  in  the  style  of 


_  , 

^\  \//>  -  3  W 

JNj  _  If  the 


Water  from 
the  feed  piphxj. 


n 


E 

:nd  floor. 


To  canalisation. 


To  canalisation. 

FIG.  108. 


the  guiding  paddles  in  turbines.     The  grain  falls  out  of  the  spout  M  on 
the  cone,  while  the  water  flows  out  of  tank  No.  4  down  the  tube  E  under 


CHAP,  in]  FLOUR   MILLING  123 

a  pressure  of  up  to  0'35  atm.  Impelled  in  this  manner,  the  water,  in 
passing  between  the  guiding  paddles  and  gyrating  as  in  a  vortex,  encoun- 
ters the  grain  which  rolls  down  the  slopes  of  the  cone. 

Tank  No.  2  is  also  named  the  stoning  tank,  for  the  stones,  overcoming 
the  pressure  of  water,  fall  to  the  bottom,  while  the  grain  is  washed 
over  the  rim  of  the  cylinder  on  to  the  lid  K,  and  thence  through  the 
spout  L  to  the  conveyor  B.  The  lower  end  of  the  tank  which  may 
deli ver  the  stones  through  the  cock  0  without  interrupting  the  work  of  the 
conveyor,  rests  in  the  tank  No.  1.  The  water  level  in  No.  1  depends  on 
the  degree  of  humidity  of  the  grain,  and  is  maintained  by  the  tube  W, 
which  receives  the  exhaust  water  through  the  holes  in  the  projecting  end 
and  transmits  it  to  tank  No.  3.  If  the  water  exceeds  its  level  limit,  it 
will  drain  away,  not  through  the  small  holes  in  the  sides  of  the  tube,  but 
through  the  open  upper  end.  The  level  of  water  in  No.  1  determines  the 
period  to  be  spent  by  the  grain  in  the  worm.  The  worm  B  resting  in  a 
copper  spout  with  holes  through  which  the  grain  cannot  drop,  conveys 
it  to  the  vertical  whizzer.  During  its  upward  journey,  the  grain  is  in- 
cessantly washed  by  streams  of  fresh  water  out  of  the  cocks  in  the  pipe  A, 
communicating  with  the  water-piping  or  with  a  reserve  tank.  Here  only 
is  the  removal  of  a  certain  amount  of  soaked  dirt  possible. 

The  water  circulates  in  the  following  way.  The  exhaust  water  from 
No.  1  is  conveyed  to  tank  No.  3,  and  then  taken  by  a  centrifugal  pump  G 
to  tank  No.  4,  out  of  which  tank  No.  2  receives  its  supply.  The  fresh 
water  is  conducted  from  the  water-piping  to  tank  No.  4  through  the 
tube  R.  If  the  outflow  of  water  during  the  washing  operation  exceeds 
the  inflow  of  fresh  water  from  the  tube  A,  the  deficient  quantity  is  sup- 
plied through  the  tube  R  to  tank  No.  4  ;  the  superfluous  water,  on  the 
other  hand,  is  let  out  of  tank  No.  4  into  the  canal  or  sewer  through  a  pipe 
with  an  open  funnel.  The  water-level  in  tank  No.  4,  controlled  by  the 
height  of  the  outflow-funnel,  determines  the  steady  pressure  in  tank 
No.  2.  The  tank  No.  3  and  the  pump  G  may  be  discarded,  if  the  water 
in  the  mill  is  so  cheap  as  to  allow  of  its  being  thrown  away  out  of  tank 
No.  1,  when  dirty.  In  the  conic  bottom  of  tank  No.  4  there  is  a  refuse 
tube  for  the  discharge  of  the  mud  that  settles  there. 

For  the  damping  of  grain  of  harder  kinds  Robinson  has  the  appara- 
tus shown  on  Fig.  109,  with  two  worms.  The  end  of  worm  No.  1 
is  immersed  in  the  water  of  the  tank  B.  At  the  lower  end  of  the 
worm  casing  is  a  box  in  which  the  stones  collect.  Worm  No.  1  carries 
the  grain  to  the  stone  separator  C,  described  above,  from  whence  it 
passes  to  worm  Nof  2  (the  angles  of  the  conveyor  worms  are  70°), 


124 


FLOUR   MILLING 


[CHAP,  in 


and  is  then  delivered  to  the  vertical  whizzer.  Out  of  the  general 
tank  the  water  is  supplied  by  a  centrifugal  pump  A .  Both  worms  are 
played  on  with  fresh  water  from  a  series  of  cocks. 

The  tanks  F  and  B  are  isolated  and  have  different  water  levels.  The 
drives  of  the  conveyors  and  pumps  are  clearly  marked  out.  Fig.  110 
represents  the  general  view. 

(2)  Mechanical  Removal  of  Water  from  the  Grain. — After  being  well 
dampened  the  grain  falls  through  spout  P  (Fig.  108)  to  the  vertical  whizzer 
to  remove  the  water.  This  operation  must  be  performed  very  rapidly, 
otherwise  the  water  will  penetrate  the  starchy  part  of  the  grain,  and  its 
moisture  content  will  exceed  the  normal  limit. 

Robinson's  centrifugal  or  vertical  whizzer  (Fig.    Ill)   consists  of  a 


vertical  rotating  drum  containing  beaters  arranged  spirally.  The  grain 
is  fed  in  at  the  base  of  the  drum  by  an  inclined  spout  from  the  worm 
through  the  inlet,  and  is  met  by  the  beaters  revolving  at  the  rate  of  70 
feet  per  second  (the  drum  makes  360  to  600  revolutions  per  minute). 
The  beaters  fling  the  grain  against  a  steel  casing,  perforated  to  let  the 
water  and  abraded  bran  escape.  The  grain  impelled  by  the  beaters 
hits  the  casing,  and  by  the  blow,  owing  to  the  decrease  of  the  great  velocity 
of  motion  of  the  grain,  the  coating  of  water  is  thrown  off  by  centri- 
fugal force  and  expelled  through  the  holes  of  the  casing.  This  is  the 
action  named  whizzing.  The  casing  consists  of  separate  sections,  eight 
or  more  in  number  (general  view).  For  the  retention  of  the  splashing 
water,  the  perforated  casing  is  enclosed  in  another  casing  of  solid  iron.  The 


CHAP.  Ill 


FLOUR   MILLING 


125 


spiral  lif ters  rapidly  raise  the  grain  to  the  top  and  deliver  it  through  an  out- 
let spout.  Besides  the  removal  of  water,  part  of  the  beeswing,  bran,  and 
beards  is  separated  on  the  way  up.  Consequently,  by  a  second  operation 
the  grain  is  simply  scoured,  when  thrown  by  the  lifters  against  the  casing. 


(3)  The  Drying  of  Grain. — The  most  important  stage  of  the  wet 
scouring  process  is  the  drying  of  the  grain.  It  is  dangerous  to  leave  the 
grain  with  a  moisture  above  the  normal,  for  that  would  lead  to  unfavour- 
able consequences  in  the  treatment  to  follow.  Overdrying  is  likewise  to 


126  FLOUR   MILLING  [CHAP,  in 

be  avoided,  as  the  grain  then  becomes  brittle,  and  gives  a  large  percentage 
of  broken  kernels  when  subjected  to  dry  scouring.  In  addition,  the 
bran  of  the  over-dry  grain  will  be  ground  to  bran  powder  during  the 
milling  process,  from  which  it  is  impossible  to  extract  the  flour. 

It  is  only  by  careful  experimental  treatment  of  the  grain  in  drying 
and  cooling  machines,  coupled  with  observations  on  the  moisture  of  the 
grain  to  be  dampened,  that  the  temperature  and  the  volume  of  the  drying 
air  and  the  quantity  of  grain  to  be  dried  may  be  defined.  For  this 
reason,  a  rationally  constructed  drying  and  cooling  apparatus  must  be 
adjustable  in  respect  to  the  temperature  and  volume  of  the  air  in  use, 
and  the  quantity  of  grain  to  be  treated  at  a  time. 

Robinson's  dryer  (Fig.  112),  like  machines  of  other  design,  is 
of  a  rectangular  section  (Fig.  96).  Two  sides  of  the  column  are  solid, 
while  the  other  two  consist  of  two  parallel  perforated  walls.  The  grain 
fed  in  through  hoppers  A  and  B  flows  between  those  walls,  and  is  sub- 
jected to  the  action  of  a  draught  from  the  chamber  0,  which  penetrates 
through  the  holes  in  the  walls.  The  warm  air  is  aspirated  from  the  steam 
chamber  through  the  aperture  Z  by  a  fan,  and,  after  passing  through  the 
stock,  is  exhausted  through  trunk  J '.  For  about  one-third  of  its  way 
the  grain  is  exhausted  with  cold  air  (temperature  of  the  mill  apartments) 
aspirated  by  another  fan  and  ejected  through  the  trunk  D.  At  the  warm 
air  inlet  Z,  the  column  is  divided  by  a  solid  bottom  which  prevents  the 
cold  air  from  penetrating  into  the  chamber  G. 

Before  proceeding  to  further  descriptions  of  the  construction,  the  signi- 
ficance of  cooling  the  stock  must  be  explained. 

The  temperature  of  the  drying  air,  depending  on  the  dampness  of  the 
grain,  varies  between  25°  and  60°  C.  Sometimes,  when  the  stock  is  very 
dry,  the  column  is  filled  with  air  of  the  outside  temperature  un warmed. 
In  that  case  the  functions  of  both  the  upper  and  the  lower  division  of 
the  column  are  identical.  But  when  the  temperature  of  the  air  has  to 
be  raised  to  30°-60°  C,  a  cooling  of  the  grain  is  necessary  for  the  following 
reasons.  The  dried  and  warm  grain  is  deposited  in  bins  to  be  tempered 
for  the  space  of  eight  to  twelve  hours,  to  allow  the  moisture  collected  in 
the  bran  to  spread  evenly  in  the  endosperm  as  well,  to  facilitate 
the  treatment  of  the  stock  in  dry  scouring  and  milling.  The  grain 
deposited  in  bins  without  having  been  cooled  previously,  retains  its  high 
temperature,  which  acts  detrimentally  upon  it,  because,  if  tempered 
for  a  long  time,  it  may  first  germinate,  and  secondly  the  starch  may 
become  soaked  to  a  paste.  Moreover,  during  the  conditioning  the 
bran  becomes  cooled  first,  thus  accelerating  the  process  of  evaporation 


CHAP,  in] 


FLOUR   MILLING 


121 


128 


FLOUR   MILLING 


[CHAP,  itt 


in  the 'outer  covers,  and  the  tempering  period  in  consequence  is  shortened. 
For  regulating  the  feeding   of  the   column   there  are  valve  flaps  K  in 


FIG.  112. 


B 


K 


W 


the  hoppers  A  and  B,  which  may  be  opened  wider  or  less  by  means  of  a 
crank  mechanism  M .     That  mechanism  controls  at  the  same  time  the 


FLOUR    MILLING 


129 


CHAP.    Ill] 

grain  delivery  by  a  valve  flap  L  worked  by  a  gear  wheel  and  rack  on 
the  flap.     The  opposite  end  of  the  crank  mechanism  carries  a  weight 


FIG.  113. 


to  counterbalance  the  load  of  grain  on  the  flaps  K. 

Another  dryer  and  conditioner  built  by  Robinson's  works  (Mallin- 
son's  patent),  of  a  more  complicated  construction,  is  shown  in  Fig.  113, 


130 


FLOUR   MILLING 


[CHAP,  in 


A  more  equable  drying  of  grain  is  realised  by  means  of  the  following 
appliances.  In  the  working  space  in  the  right-hand  side  of  the 
column,  there  are  vertical  spouts  fed  with  steam  from  the  heating 
chamber  E.  At  the  top,  in  the  hopper  A,  these  spouts  are  connected 


by  a  common  horizontal  trunk.  Within  the  working  space,  the  grain 
travels  in  a  zigzag  line,  owing  to  the  inclined  partitions,  thus  assisting 
the  stirring  of  the  grain.  Through  openings  in  the  partitions,  the 
warm  air  exhausted  through  the  spout  G  by  a  fan  penetrates  into  the 
stock  from  the  chamber  H.  The  vertical  steam  pipes  are  designed  to 
maintain  an  even  temperature  in  the  working  space,  for  in  the  column  of 


CHAP.    Ill] 


FLOUR   MILLING 


131 


the  first  type,  the  grain  descending  close  to  the  outer  wall  of  the  working 
space  is  treated  with  air  of  a  lower  temperature,  and  is  consequently  less 
dried  than  the  grain  travelling  close  to  the  inner  wall. 

On  leaving  the  right-hand  side  division  of  the  column  the  grain  flows 


through  the  feeder  B  into  the  left  division  which  is  not  heated  by  steam 
pipes.  This  part  of  the  column  in  its  upper  range  operates  with  air  from  the 
general  chamber  E,but  in  its  lower  part  the  grain  is  cooled  from  the  trunk  N. 

The  dryers  and  coolers  of  various  constructions  will  be  compared  later. 

Washers  by  Turner,  H.  Simon,  Briddon  and  Fowler,  &c.  The 
Damping  of  Grain. — A  damping  machine  of  another  type  (Fig.  114) 


132 


FLOUR   MILLING 


[CHAP,  in 


is  the  English  machine  for  washing  coke,  slightly  modified.  The 
machine  consists  of  a  tank  divided  into  six  sections,  in  which  the 
water  circulates  in  the  following  manner. 

The  fresh  water  playing  the  grain  is  delivered  through  holes 
in  the  piping,  and  collecting  in  No.  1  (Fig.  115)  is  pumped  along  the 
tube  d  to  the  chamber  F  by  a  centrifugal  pump  C  ;  from  F  it  flows  over 
into  No.  5  and  No.  6,  two  vessels  communicating  with  each  other 
(Fig.  116)  ;  out  of  Nos.  5  and  6  the  water  fills  No.  4,  which  likewise  has 


Section  through  EF. 


FIG.  116. 

a  connecting  channel.  In  this  manner,  divisions  Nos.  1  and  2  separated 
from  Nos.  3,  4,  5  and  6  have  a  communicatory  opening  b,  while  the  dirty 
water  flows  out  of  No.  2  through  the  pipe  g.  The  divisions  Nos.  5  and  2 
(Fig.  117)  are  covered  on  different  heights  with  perforated  screens  ;  Nos.  6 
and  4  encase  wooden  pistons  ra  and  /  driven  by  an  eccentric.  During  the 
operation  of  the  machine  these  pistons  agitate  the  surface  of  the  water 
over  the  perforated  lid,  giving  from  180  to  200  vibrations  per  minute. 

The  work  is  performed  as  follows  :  the  grain  is  fed  into  worm  C 
in  the  stream  of  water.  Then  it  is  carried  by  the  worm  to  the  hopper, 
whence  the  feed  roller  r  passes  it  on  to  the  surface  of  the  screen  of  division 


CHAP.   Ill] 


FLOUR   MILLING 


133 


PLAN    OF   H.    SIMON'S   WASHING  MACHINE. 


Section  through  AH 


SECTION    THROUGH    A  B. 
FlG.    117. 


134  FLOUR   MILLING  [CHAP.  Hi 

No.  5,  where  the  vibrating  stream  washes  it  away  to  the  overflow  p,  and 
further  to  the  lower  end  of  conveyor  B.  In  travelling  to  the  overflow  p 
the  grain  passes  over  division  No.  3  with  a  lowered  screen  and  leaves  the 
heavy  extraneous  matter  (stones,  &c.)  on  it,  so  that  No.  3  serves  as 
a  stoner. 

To  prevent  a  heavy  overflow  of  water  being  pumped  from  the  chamber  F 
into  division  No.  5,  there  is  a  funnel-shaped  opening  in  F  over  the  water 
inlet,  which  is  the  end  of  the  tube  supplying  No.  4  with  water.  Owing 
to  this  tube  the  water  level  in  Nos.  5  and  6  is  kept  at  about  the  same  height. 

The  washing-machine  just  examined  (H.  Simon's)  has  two  worms, 
though  it  may  be  provided  with  but  one,  B  (Turner's  machine).  In  the 
latter  case  the  grain  is  fed  straight  into  the  hopper,  and  thence  to  division 
No.  5. 

We  must  point  out  some  defects  of  this  machine  before  proceeding 
to  describe  whizzing  and  drying  machinery  of  other  makes.  The 
mistake  the  makers  of  these  machines  make,  lies  in  their  supposing 
the  washing  of  grain  to  be  the  chief  function  of  the  machine.  That  is 
why  its  construction  is  complicated  by  the  divisions  Nos.  5  and  3  in  the 
tank  with  vibrating  surfaces. 

This  principle  is  adaptable  in  the  case  of  coke,  a  porous  substance, 
which  is  indeed  washed  by  the  water  impelled  into  the  pores  by  strokes. 
As  to  the  grain,  all  it  needs  is  to  be  well  damp.  The  grain  must  not 
be  immersed  for  longer  than  thirty  to  forty  seconds,  which  is  not  a  long 
enough  period  for  the  dirt  firmly  sticking  either  to  the  surface  of  the  grain, 
or  in  its  crease,  to  be  washed  off. 

A  vibratory  mechanism  is  therefore  not  required.  If,  on  the  other 
hand,  the  agitation  of  the  water  surface  is  to  be  abolished,  it  is  evident 
that  Robinson's  type  of  washing-machine,  or  one  akin  to  it,  must  be 
adopted. 

Besides  this  essential  defect,  resulting  from  a  misunderstanding  of  the 
principle  of  the  machine,  faults  in  construction  must  be  mentioned. 
A  wish  to  make  the  machine  solid  induced  the  engineers  to  utilise  the 
pressure  of  the  pump  in  driving  the  grain  to  the  overflow.  This  results 
in  a  fluctuation  of  the  water  levels,  in  spite  of  the  tube  e  devised  for  the 
compensation  of  the  strokes.  The  opening  in  the  partition  between  No.  1 
and  No.  2  regulates  the  water  level  of  No.  1,  but  violates  the  principle  of 
counter  current  (dirty  water  washing  dirty  grain),  for  there  is  a  possibility 
of  the  dirty  water  being  exhausted  through  the  opening  out  of  the  divi- 
sion No.  2. 

The  Removal  of  Water  from  the  Grain. — As  regards  the  separation  of 


CHAP,  in] 


FLOUR   MILLING 


135 


water,  H.  Simon's  centrifugal  whizzer  (Fig.  117)  in  its  constructive  basis 
differs  in  no  respect  from  that  of  Th.  Robinson's. 

A  few  general  remarks  have  to  be  made  concerning  the  whizzing 
process. 

There  exist  two  types  of  whizzing  or  centrifugal  machines  having 
more  or  less  important  differences  in  the  construction  of  their  lifters. 
The  first  is  Robinson's  type,  where  separate  paddles  disposed  in  a  spiral 
line  play  the  part  of  lifters,  or  that  of  Seek  (Fig.  118),  which  has  lifters 


FIG.  118. 


FIG.  119. 


arranged  on  a  generating  line,  and  of  a  saw-like  shape,  with  teeth  bent  to 
one  side,  also  in  a  spiral  line.  The  lifters  in  the  second  type  of  machinery 
(Fig.  119)  are  set  at  an  angle  to  the  generating  line  of  the  cylinder,  as  in 
scouring  machines.  In  this  case  not  only  the  wide  flanged  blades,  but 
the  whole  lifter  is  employed  in  elevating  the  grain  (the  construction 
belongs  to  the  Italian  works  of  S.  A.  Meccanica  Lombarda). 

Of  a  much  greater  significance  is  the  position  of  the  rotatory  axis  of 
the  lifter  drum,  which  is  either  horizontal  or  vertical.  In  the  former 
case,  the  whizzer  is  placed  so  as  to  receive  the  grain  together  with  the 
water  out  of  the  stone- separating  and  the  washing  apparatus.  There- 
fore, the  lifters  in  taking  the  grain  scoop  up  the  water  at  the  same  time. 


136 


FLOUR   MILLING 


[CHAP,  itt 

Under  such  circumstances  the  grain  is  certainly  well  rinsed,  but  this 
process  is  somewhat  dangerous,  because  the  grain  may  remain  in  the 
water  for  too  long  a  time,  so  that  the  starchy  part  may  absorb  too  much 
moisture.  For  this  reason  horizontal  whizzers  are  gradually  dropping 
out  of  use. 

The  grain  is  generally  fed  into  the  whizzer  after  the  water  has  been 


FIG.  120. 

drained  off.  Some  engineers  wish  not  only  thoroughly  to  soak  the 
grain,  but  actually  to  wash  it.  In  this  respect  the  washing  pro- 
cess of  the  firm  of  "  Seek  Bros."  (Fig.  120)  deserves  attention.  Here 
we  have  the  full  process.  From  the  stoner  A  the  grain  and  water 
flow  into  the  first  whizzer  B.  At  the  bottom  of  the  apparatus  the 
grain  is  well  rinsed  in  the  second  apparatus  C.  If  the  time  is  accu- 
rately calculated,  this  process  _  may  bring  good  results.  Yet  the 


CHAP.   Ill] 


J^LOUR    MILLING 


137 


engineers  ought  not  to  concentrate  their  whole  attention  on  the  washing 
of  the  grain,  but  should  remember  that  we  have  here  an  example  of  the 
process  of  scouring  by  washing. 

Fig.  121  represents  the  washing  plant  from  the  works  of  Luther.  Here 
1  is  a  bin,  2  a  stone  separator,  3  a  rinsing  appliance,  4  a  centrifugal 
pump,  5  a  vertical  whizzer,  6  a  dryer,  7  a  collecting  funnel,  8  a  hot  air 
exhaust,  9  a  cold  air  exhaust,  10  the  heating  chamber,  11  a  dirt 
collector,  12  a  dryer,  13  a  delivery 
pump,  14  a  water  cistern,  and  15 
a  dust  collector. 

The  Drying  of  the  Grain. — In 
drying  grain,  that  most  important 
stage  in  the  wet  scouring  process, 
the  selection  of  the  type  of  drying 
apparatus  is  a  very  serious  ques- 
tion. In  the  first  place,  we  must 
acknowledge  that  the  most  active 
agent  in  the  drying  process  is  the 
air.  This  absorbs  the  greater  a- 
mount  of  water- vapour,  the  higher 
is  its  temperature,  and  the  smaller 
the  pressure.  The  absolute  quan- 
tity of  the  vapour  absorbed  by  the 
air  is  proportionate  to  its  volume. 
It  follows,  therefore,  that  an  effi- 
cient, i.e.  rapid,  drying  demands  : 

(1)  The  highest  temperature. 

(2)  A  pressure  below  that  of 
the  atmosphere. 

(3)  The  greatest  possible  quan- 
tity of  working  air. 

These  three  conditions  are  defined  by  the  duration  of  the  drying 
process.  The  faster  the  drying  is  to  be  performed,  the  higher  must  be 
the  temperature,  the  more  rarefied  the  air,  and  the  larger  the  quantity 
of  it  used.  On  the  other  hand,  given  the  limit  of  significance  of  the 
temperature  and  pressure,  and  the  air  consumption,  we  are  enabled 
to  define  the  length  of  the  drying  procedure  and  the  amount  of  grain, 
according  to  .its  primary  and  final  moisture. 

An  experimental  drying  of  moist  grain  has  shown  that  the  highest 
limit  of  temperature  is  60°  C.  If  that  limit  is  exceeded,  the  bran  as 


FIG.  121. 


138 


FLOUR   MILLING 


[CHAP,  in 


well  as  the  kernels  burst.  However,  as  far  as  possible  high  tempera- 
tures ought  to  be  avoided,  because  firstly,  when  heated  to  60°  C. 
the  starch  may  turn  to  paste,1  and  secondly,  a  lower  drying  temperature 
requires  less  fuel. 

These   two   circumstances   suggest   the   necessity   of   using   rarefied 
air.      And  the  best  result  is  actually  obtained  by  drying  the  stock  in 

rarefied  air,2  as  is  done  in  large 
granaries.  However,  such  enormous 
structures  as  a  vacuum  drying 
apparatus  of  E.  Passburg's  are  im- 
possible in  mills,  because  we  have 
a  washing  plant  which  must  be 
included  in  the  cycle  of  machinery 
belonging  to  the  grain  -  clean- 
ing department,  and  space  is 
limited. 

We  have  two  types  of  dryers 
for  drying  the  grain  in  the  wet 
scouring  process  :  (1)  operating  by 
forced  air,  and  (2)  by  aspirated,  i.e. 
rarefied  air. 

The  Robinson  dryer  we  have 
examined  operates  by  rarefied  air. 
"V  scraper  Fig.  122  shows  o>  type  of  dryer 
(Turner's  works  in  Ipswich)  working 
with  forced  air.  Nearly  all  European 
and  American  milling  engineers 
favour  the  second  type  of  dryers. 

On  Fig.  123  we  have  a  drying 
arrangement  of  Simon's  (known 
under  the  name  of  "  Biihler  Bros." 
in  Russia).  Here  A  is  the  air- 
heating  chamber,  T1  a  fan  im- 
pelling the  warm  air  into  the  trunks  B-B,  and  T  another  fan  filling 
the  trunks  with  cold  air.  Engineers,  however,  should  avoid  build- 
ing dryers  which  work  by  forced  air,  i.e.  with  increased  pressure. 
Besides  considerations  respecting  greater  security  and  economy  in 
drying,  there  are  considerations  in  regard  to  their  construction. 


Inner  &  outer 


cylinde 
perforated  metal 


Delivery  spout 


1  Profs.  Kick  and  Zworykin  set  the  limit  at  60°,  F.  Baumgartner  at  55°. 

2  Vacuum  drying  apparatus  of  E.  Passburg's  system,  Russian  Miller,  1909,  No.  10. 


CHAP.   Ill] 


FLOUR   MILLING 


139 


Though  the  apparatus  may  be  fitted  up  perfectly,  there  is  always  a 
possibility  of  the  dust  penetrating  into  the  crevices  if  the  dryer  operates 
by  forced  air.  Its  inspection  is  very  much  hindered  by  the  fact  of  the 
dust  blowing  into  the  apparatus  through  the  window  when  it  is 
opened.  Now,  if  the  machine  works  with 
aspirated  air,  these  defects  cannot  obtain 
in  the  process. 

In  the  second  type  of  dryer  from  the 
works  of  Robinson  (Fig.  113)  we  see  that 
its  right-hand  working  part  is  heated  by 
steam-pipes  which  are  adapted  for  the 
purpose  of  completely  removing  the  mois- 
ture with  the  aid  of  a  higher  temperature. 
It  must  be  kept  in  mind,  however,  that  in 
employing  such  a  construction  we  run  the 
risk  of  choking  the  grain  which  moves  in 
the  neighbourhood  of  the  tubes.  Besides, 
the  air  pipe  which  supplies  the  left  part 
of  the  column  with  cold  air  is  warmed 
by  the  hot  air,  an  undesirable  effect.  In 
this  column  the  adaptation  of  a  step  par- 
tition, owing  to  which  the  stock  travels 
in  zigzag  line  and  becomes  mixed,  must 
be  acknowledged  to 
be  useful;  it  also 
promotes  a  more 
equable  drying  of 
the  grain. 

Touching  modern 
grain-drying,  Pro- 
fessor Zworykin 
suggests  a  few  very 
interesting  consi- 
derations as  to  the 
principle  and  the 
construction.  He  finds  the  following  defects  in  the  dryers  just  spoken  of  : 

(1)  The  stock  which  travels  along  the  vertical  canal  on  the  side  of 
the  drying  air  inlet  is  dried  more  thoroughly  than  the  stock  moving  on 
the  opposite  side  of  the  canal. 

(2)  The  grain  flowing  down  the  central  part  of  the  drying  canal 


FIG.  123. 


140 


FLOUR  MILLING 


[CHAP,  m 


Wet  grain 


moves  faster  than  the  grain  on  either  side  of  it,  and  is  consequently 
dried  to  a  different  degree. 

(3)  The  air,  during  the  drying  process,  in  passing  through  a  thin 
layer  of  grain  equal  to  the  breadth  of  the  drying  canal  is  not  saturated 
enough  with  moisture,  and  is  therefore  insufficiently  utilised. 

As  concerns  the  two  first  defects,  they  are  effectually  done  away 
with  in  Mallinson's  dryer  with  step-canals.     This  is  confirmed  in  the 
types  of  machinery  suggested  by  Professor  Zworykin.     The  third  defect 
is  to  be  overcome  by  the  principle  of  counter-currents  adapted  by  Pro- 
fessor Zworykin  in  the  following  two  sketches 
of  drying  columns. 

Fig.  124  represents  a  hollow  column  AB  of 
a  square  or  rectangular  section  provided  with 
a  series  of  jutties  of  a  triangular  section  in- 
side (1,  2,  3,  4,  5,  6,  7,  8,  9,  10)  and  a  hopper 
D  at  the  top,  which  contains  a  feed  roll  C  and 
an  arrangement  for  regulating  the  feeding. 
The  moist  grain  passes  through  the  hopper 
and  the  feeding  apparatus  into  the  column, 
rolls  down  the  jutties  (1,  2,  3,  4,  .  .  .  10),  as 
pointed  by  whole  arrows,  and  is  discharged 
through  the  valve  K  below.  In  the  direction 
opposite  to  its  course  a  current  of  air  is  driven 
through  the  inlet  E  :  it  ventilates  the  grain 
several  times  at  the  moment  it  falls  from  the 
even  on  to  the  odd  jutty  or  vice  versa,  and 
then  humid  with  the  moisture  drawn  off 
the  grain,  it  passes  to  the  fan  through  the  outlet  Z.  Naturally  the 
grain  must  flow  in  a  thin  layer  and  must  not  block  up  the  space. 

For  the  action  to  be  regular,  Professor  Zworykin  recommends  heat- 
ing all  the  jutties  or  only  one  side  of  them  with  steam  or  water,  while 
the  period  spent  by  the  grain  in  the  apparatus  may  be  regulated  by 
making  at  least  one  range  of  boxes  (for  instance,  the  even  numbers) 
adjustable  so  as  to  alter  the  angle  of  inclination  of  the  surfaces  down 
which  the  grain  rolls  from  45°  to  70°.  In  Professor  Zwory kin's  opinion, 
there  is  no  especial  need  artificially  to  cool  the  dried  grain,  if  after 
drying  it  is  not  to  be  tempered  in  bins,  but,  continually  passes  from 
machine  to  machine,  and  undergoes  a  gradual  treatment. 

The  second  variation  of  that  design  is  a  round  cylindrical  column 
with  conic  (Fig.  125)  surfaces  B.  The  central  part  A  of  the  apparatus 


Dry  ffrai 

FIG.  124. 


141 


Grain  inlet 


CHAP,  m]  FLOUR   MILLING 

is  heated.  The  grain  flowing  through  the  hopper  travels  over  the  conic 
surface  of  the  heated  central  part  A,  and  aspirated  on  its  way,  falls  on 
the  conic  surface  B.  Then  it  rolls  off  B  on  to  the  second  cone  A  and  is 
again  fanned,  &c.,  till  it  reaches  the  outlet. 

Calculations  in  Reference  to  Dryers.  —  An 
approximate  computation  of  the  quantity  of 
air  and  heat  required  for  drying  purposes  may 
be  based  on  the  following  considerations  :  x 

If  the  capacity  of  the  dryer  is  stated  to 
be  P  kilogramme  of  grain  per  hour,  the 
quantity  of  water  to  be  extracted  from  the 

grain  in  one  hour  will  be  defined  in     ^~ffo) 

100 

kilogramme,  where  p  signifies  the  per- 
centage of  moisture  in  the  damp  grain,  and 
Po  in  the  dried  grain. 

Each  cubic  metre  of  air  extracts  y 
kilogramme  of  moisture,  consequently  the 

drying  of  the  stated  quantity  of  grain  requires      ^  " 

of  air.  The  quantity  of  water-vapour  which  a  cubic  metre  of  air  may 
hold,  when  fully  saturated,  depends  on  the  temperature,  and  is  given  in 
kilogramme  weight  in  the  following  table  : 

TABLE  XV 


cubic  metres 


Degrees 
C. 

Weight  of  Vapour, 
Kilogramme. 

Degrees 
C. 

Weight  of  Vapour, 
Kilogramme. 

Degrees 

Weight  of  Vapour, 
Kilogramme. 

-30 

0-00074 

-5 

0-00368 

20             0-0171 

-25 

0-00095 

0 

0-00497 

25            0-0281 

-20 

0-00129 

5 

0-00676 

30            0-0301 

-15 

0-00189 

10 

0-00935 

40 

0-0509 

-10 

0-00268 

15 

0-01275 

50            0-0830 

60 

0-1306 

If  the  air  entering  the  dryer  contains  k  per  cent,  of  moisture  and  its 
temperature  is  T,  on  leaving  the  apparatus  it  is  not  perfectly  saturated, 
having  k  per  cent,  of  humidity  and  t°  temperature.  Then  the  total 
quantity  of  moisture  y  absorbed  by  1  cubic  metre  of  air  in  relation  to 
the  temperature  of  air  after  usage,  t°,  is  formulated  thus  : 

kl 


-*•    v  r 

'The  Grain  Dryer,"  by  Prof.  K.  Zworykin,  Russian  Miller,  1910,  No.  11. 


142  FLOUR   MILLING  [CHAP,  m 

where  I  and  10  signify  the  quantity  of  steam  in  kilogrammes  saturating 
1  cubic  metre  of  air  having  a  temperature  of  T  and  t0  respectively,  while 
a  is  the  coefficient  of  expansion  of  the  air,  equal  to  0*003665.  Hence  the 
formula  defining  the  volume  of  air  required  for  drying,  in  cubic  metres 
at  a  temperature  t0  : 


kl 


The  term  .  —  ^-  is  insignificant  if  cold  air  is  employed,  and  in  a 

L  -\-a(tQ      J.  ) 

rough  calculation  may  be  left  out  ;  and  the  quantity  K0  does  not  exceed 
0*7,  for  the  dampness  of  the  air  discharged  is  assuredly  not  to  be  increased 
beyond  70  per  cent,  of  the  absolute  dampness. 

Assuming  the  temperature  of  the  medium  supplying  the  air  to  be  10°  C., 
the  temperature  of  heating  and  at  the  discharge  of  the  air  60°  C.,  the  per- 
centage of  moisture  in  the  air  in  both  cases  is  70  per  cent.,  the  primary 
dampness  of  the  grain  30  per  cent.,  and  10  per  cent,  when  dry,  after  due 
substitution,  the  formula  of  V  will  be  presented  as  follows  : 

_  30-10  _  _,_  1  ,       1 

v/n-7   n.iqofi  0-7.0-00935        d"5  .  0-7  .  0-1305-I-0-045 

"1+0-003665(60-10)) 
-|-2|  cubic  metres  at  60°  C.  of  temperature. 

To  define  the  quantity  of  warmth  required  in  the  drying  process,  it 
must  be  known  how  much  warmth  is  needed  for  the  moisture  to  evaporate 
from  the  grain,  and  for  the  heating  of  the  grain  and  the  air  supplied  out 
of  medium,  to  the  temperature  it  has  when  leaving  the  dryer.  That 
quantity,  Q0,  is  defined  as  : 

+  V0d0c0(t0-T). 

Here  cx  is  the  specific  heat  of  the  grain  amounting  to  about  0'6  ;   c0  that 
of  the  air  under  steady  pressure,  equal  to  0'237  ;  and  d0  the  weight  of 
1  cubic  metre  of  air  heated  to  60°  C.,  equal  to  1*06  kilogrammes. 
Substituting  these  significations  in  Q,  we  have  : 

#0=i(606-5+0-305  .  60-10)+t(60-10)c1+2'25  .  50  .  T06  .  0'237. 
o  o 


.  T06 


So,  under  the  conditions  alluded  to,   1  kilogramme  of  dried  grain 
demands  the  expenditure  of  about  175  units  of  heat.     Once  the  heat 


CHAP,  m]  FLOUR    MILLING  143 

expenditure  is  known,  it  is  easy  to  calculate  the  quantity  of  fuel  consumed 
by  the  heating  source  of  any  one  particular  machine. 

Professor  Zworykin  attaches  much  importance  to  the  principle  of 
counter- currents,  wishing  to  utilise  the  absorbing  capacity  of  the  air  to 
its  utmost  within  the  bounds  of  possibility.  The  adaptation  of  this 
principle  to  grain  drying  in  the  wet  scouring  process  is  not  defensible, 
because  the  coefficient  of  the  best  results  in  drying,  in  the  pre- 
sent case,  is  defined  not  by  the  greatest  saturation  of  the  air,  but  by 
a  more  rapid  drying  of  the  bran.  If  we  accept  the  principle  of 
counter- currents  as  basis  for  grain  drying  in  the  wet  scouring  process,  the 
gradually  drying  grain  will  not  shell  in  the  column  apparatus,  a  fact 
mentioned  at  the  commencement  of  our  explanation  of  the  wet  scouring 
process. 

Before  ending  the  discussion  of  grain  scouring  by  washing,  mention 
must  be  made  of  the  fact  that  by  far  the  greater  number  of  European 
works  favour  the  Robinson  type  of  washing,  or  rather  stone-separating 
machine. 

Vertical  whizzers,  further,  very  often  receive  the  grain  together  with 
the  dirty  water  (the  works  of  Kapler,  Daverio,  Seek,  and  several  others). 
Lastly,  the  dryers  of  all  the  works,  except  that  of  Robinson,  operate  with 
forced  air. 

As  regards  the  consumption  of  energy,  fuel,  and  water  in  the  wet 
scouring  process,  it  is  to  be  noted  that  the  plants  of  the  Robinson,  Luther, 
and  similar  types,  are  in  all  respects  more  economic  than  the  Simon  or 
Turner  type.  The  first  cost  and  working  expenses  of  the  wet  scouring 
process  are  considerably  greater  than  in  the  usual  dry  grain  cleaning, 
but  the  improvement  of  the  medium  and  the  lower  grades  of  flour  covers 
the  expenses  over  and  over  again. 

The  expenditure  of  water  in  the  wet  scouring  process  amounts  to  from 
4'0  to  4' 9  gallons  for  1  bushel  of  grain  in  plants  where  the  dirty  water 
is  returned  to  repeat  its  work  (to  the  pressure  tank  by  the  principle  of 
counter-currents),  and  12  gallons  for  1  bushel  when  working  constantly 
with  fresh  water. 

VI 
DAMPING  THE  GRAIN 

When  the  grain  reaches  the  milling  department  it  is  important  that 
the  offal  particles  should  not  be  reduced  to  a  fine  dust  together  with  the 
stock.  It  is  impossible  to  extract  finely  ground  offals  from  flour.  But 


144 


FLOUR   MILLING 


[CHAP,  in 


if  the  bran  coat  is  broken  up  into  particles  larger  than  the  flour,  they  may 
be  removed  by  bolting.  It  is  of  great  consequence,  therefore,  that  the 
process  of  milling  should  be  performed  so  as  to  leave  the  bran  coats  whole. 
If  we  have  dry  grain  during  the  milling  process,  the  dried  bran  is 
very  easily  ground  to  dust  which  mixes  with  the  flour.  If,  on  the  other 
hand,  we  dampen  the  bran,  it  becomes  more  elastic  and  offers  greater 
resistance  to  pulverisation  than  the  starchy  mass  of  the  grain. 

In  that  case  the  force  sufficient  to  break  the  kernel  will  leave  the  bran 

coats  intact.     If  an  elasticity  is  to  be  imparted  to  the  bran,  it  is  necessary 

to  temper  it.     Naturally,  a  damping  is  needed  only  when  the  grain  is 

dry,  and  in  its  process  of  cleaning  has  not  been  scoured  by  washing. 

The   damping  of  the   bran  of  the   dry  grain  in  the  dry  process  of 

cleaning   is    performed  (if 
~  the    grain    is    very     dry) 

either  previous  to  the 
second  scouring,  or  be- 
fore it  is  fed  into  the 
first  break  roll.  In  the 
first  case,  the  bran  en- 
velops the  grain  so  closely 
that,  without  breaking  it 
up,  it  cannot  be  re- 
moved ;  when  softened  by 
water,  it  is  separated 
with  greater  ease.  In  the 

second  case,  the  elasticity  of  the  dampened  bran  resists  the  triturating 
effect  of  the  grinding. 

There  are  two  types  of  apparatus  for  conditioning  the  bran  :  (1)  the 
wetting  apparatus,  and  (2)  the  apparatus  for  steaming  the  grain. 

Damping. — The  grain  is  wetted  with  the  aid  of  an  apparatus  (Fig.  126) 
which  consists  of  a  paddle-wheel  resembling  the  overshot  water-wheel, 
set  in  an  iron  casing  A.  The  grain  fed  through  a  spout  hopper  a,  as 
marked  by  arrow  s,  falls  on  the  paddles  and  brings  the  wheel  into 
rotation.  The  motion  is  communicated  through  gear  wheels  b-c  to  the 
wheel  D  which  carries  a  series  of  cups  d  drawing  up  water  out  of  the 
cistern  B.  On  reaching  a  certain  height  the  water  pours  out  of  the 
cups  into  a  long  inclined  trough  E,  down  which  it  runs  and  is  spouted 
through  tube  e  (arrow  s2)  on  to  the  grain,  which  on  leaving  the  paddle- 
wheel  has  passed  through  the  conveyor  and  is  now  flowing  (arrow  s-^) 
to  the  bin.  The  tank  B  is  filled  from  the  water-piping  along  s.3.  If  the 


FIG.  126. 


CHAP.    Ill] 


FLOUR    MILLING 


145 


FIG.  127. 


consumption  of  water  is  low,  its  overflow  runs  out  of  B  down  tube  / 
set  on  a  certain  level.     The  inflow  of  water  is  regulated  automatically  : 
when  the  flow  of  grain  diminishes,  the  revolving  velocity  of  the  paddle- 
wheel  diminishes  also,  and  consequently  that  of 
wheel  D,  thus  reducing   the  water  supply  to  B. 
With  the  stoppage  of  the  feeding  of  grain,  the 
work  of  the  wetting  apparatus  is  discontinued. 
The  water  flowing  to   B  flows   out   at  /,  which 
gives    the    sign   to    those    attending    the    grain- 
cleaning  division. 

Another  less  cumbrous  apparatus  is  shown  in 
Fig.  127.  Here  the  conic  cups  a  are  screwed  on  to 
tubes  r/i.  The  water  scooped  up  by  these  boxes  is 
conveyed  by  pipes  d1  to  6,  whence  it  pours  into  the 
box  c  :  from  e  the  water  flows  to  the  box  d  and 

then  along  the  pipe  sx  falls  on  the  grain  in  the  worm  conveyor  A,  which 
is  carrying  it  by  the  way  of  <s2  to  the  bin.  Owing  to  a  stirring  action 
of  the  worm,  a  more  or  less  even  dampening  of  the  grain  is  effected. 

Steaming. — However  energetically  the  mixing  be 
performed,  still  the  whole  stock  is  not  moistened 
to  an  equal  degree.  With  the  view  to  making  the 
tempering  of  the  bran  more  efficient,  the  Americans 
suggest  steaming  the  grain. 

Fig.  128  shows  Beall's  steaming  apparatus;  its 
shape  is  cylindrical,  with  steam  circulating  between 
its  double  walls.  Its  mode  of  action  is  as  follows  : 
Through  the  hopper  6  the  grain  is  fed  into  the 
inner  cylinder,  where  it  falls  on  the  bottom  disc  5 
with  star-shaped  perforations. 

The  flow  of  grain  is  regulated  by  a  cone  8,  which 
is  fixed  in  the  cylinder  by  a  cross-head  7.  The 
stream  of  grain  is  controlled  by  a  cylindrical  gate  6 
fastened  to  the  same  rod  9  on  .which  the  disc  5  is 
set,  and  which  rests  on  a  spring  4.  If  a  large  quan- 
tity of  grain  has  collected  on  the  disc  5,  the  gate  6 
stops  the  passage  of  grain  between  the  cone  and  its  rim.  Proportionately 
to  the  outflow  of  grain,  the  weight  diminishes  and  then  the  spring  4 
begins  to  act  :  it  lifts  the  rod  and  opens  the  gate.  The  steam  circulates 
in  the  following  manner.  The  steam,  which  is  generally  exhaust  steam, 
is  let  into  the  space  between  the  two  walls  of  the  cylinder  through^the 


FIG.  128. 


146 


FLOUR    MILLING 


[CHAP,  in 


tube  1,  its  passage  being  controllable  by  a  valve  a.  The  steam  enters 
into  the  working  space  by  inlets  3,  warming  the  inner  cylinder  on  its  way 
(the  outer  one  is  insulated).  Part  of  it  condenses  on  the  grain,  while 
the  rest,  becoming  cooled,  sinks  and  is  delivered  through  the  lower  outlets 
into  the  intercylindric  space,  whence  it  is  discharged  through  the  tube  2. 
But  more  often  there  are  no  apertures  below,  and  all  the  steam  becoming 
condensed,  dampens  the  stock  still  more.  The  steam  cooled  in  the 
intercylindric  space  passes  out  through  the  tube  2. 

The  main  point  in  the  steaming  process  is  the  warming  of  the  grain 
in  the  cylinder.  The  moisture  contained  in  the  kernel  of  the  berry 
evaporates  and  is  detained  by  the  skin.  i.e.  the  grain  "  sweats." 


Water  and 


FIG.  129.  FIG.  130. 

In  addition,  the  condensing  steam  settles  on  the  surface  of  the  grain 
and  moistens  it  in  an  even  measure. 

Another  steaming  apparatus  is  shown  in  Figk  129.  Here  the  gate  A 
opens  under  the  weight  of  the  grain.  The  cross-beams  B  serve  as  guides 
to  the  rod  a,  which  is  connected  with  a  small  lever  b  rotating  in  a  ball 
bearing,  owing  to  the  presence  of  a  ball  close  to  the  centre  c.  The  other 
end  of  the  lever  b  is  joined  to  the  rod  e  moving  in  the  solid  journal  bear- 
ing /  provided  with  a  spring.  By  means  of  a  hand- wheel  d  the  slide 
valve  A  is  opened  to  its  utmost.  When  the  flow  of  grain  is  discon- 
tinued, the  spring  /  pushes  the  rod  e  which  turns  the  lever  b,  thus  lifting 
the  rod  a  and  stopping  the  spout  with  the  gate. 

In  the  more  simple  steaming  apparatus  "  Eureka  "  only  the  middle 
part  of  the  cylinder  is  heated  (Fig.  130).  The  flow  of  grain  here  is 


CHAP,  in]  FLOUR    MILLING  147 

regulated  non- automatically.  The  stock  passes  through  the  cone  A 
between  a  conic  gate  F.  Owing  to  the  rotatory  motion  of  a  part  of  the 
spout  B  the  gate  set  on  a  rod  having  a  square  lower  end  and  the  upper 
one  furnished  with  a  screw  thread,  rises  or  falls,  thus  altering  the  useful 
area  between  the  cones  A  and  F. 

The  adoption  of  the  steaming  apparatus  produced  excellent  results, 
and  therefore  every  large  American  mill  uses  it  instead  of  the  wetting 
system.  The  capacity  of  these  machines,  according  to  their  size,  varies 
from  25  to  60  bushels  per  hour. 

Apparatus  having  no  flow  regulator  are  so  simple  that  any  tin- 
smith can  make  them. 

After  steaming  it  is  advisable  to  let  the  grain  temper  in  bins  for 
1  to  H  hours. 


VII 

GRAIN-CLEANING  DIAGRAMS 

In  the  preceding  chapters  we  have  examined  all  the  machines  and 
apparatus  of  the  grain-cleaning  department.  Now  the  order  of  sequence 
of  the  cleaning  machinery  of  both  the  dry  and  the  washing  systems  has 
to  be  considered. 

In  our  diagrams  the  cleaning  of  wheat  and  rye  will  be  con- 
sidered. 

We  shall  begin  with  the  most  simplified  flowsheets,  gradually  proceed- 
ing to  the  more  modern  forms  of  cleaning. 

Dry  Gleaning.  1.  Simplified  Cleaning. — Here  we  have  in  view  the 
diagrams  for  a  simple  roller  system  producing  two  to  three  kinds  of 
flour.  The  cleaning  tackle  must  be  cheap,  therefore  it  is  best  to  adopt 
combined  machinery  :  a  grain-cleaning  machine  of  the  Zolotuchin  type 
(see  p.  114)  and  a  wetting  machine  will  suffice,  if  the  grain  is  very  dry. 
The  wetting  can  be  simplified  by  taking  a  water-barrel  and  setting  into 
it  a  cock  with  a  draining  pipe  leading  to  the  conveyor. 

The  order  of  machinery  in  the  improved  style  of  cleaning  will  be  as 
follows  : 

(1)  A  separator  with  a  sieve  (preferably  with  two  sieves  for  large  and 
small  impurities),  (2)  a  cockle  separator,  (3)  a  combined  machine  of  the 
Zolotuchin  (Fig.  104),  American  (Fig.  103),  or  Schneider,  Jacquet  &  Co. 
(Fig.  94)  type,  (4)  a  wetting  machine. 

£,  4    Medium    Type   of   Cleaning. — The   cleaning   process   is   more 


148 


FLOUR    MILLING 


[CHAP,  in 


Grain  from  storing  bin 
18 


AITS 


elaborate  here,  because  it  aims  at  a  more  perfect  separation  of  impurities 
and  beeswing.     The  machines  and  apparatus  to  be  employed  are  : 

(1)  A  bolting  machine  for  large  and  small  refuse  (reel  separator, 
bolting  separator,  aspirator,  or  zigzag  separator),  (2)  a  cockle  separator, 
(3)  a  controlling  trieur,  (4)  a  magnet  apparatus,  (5)  first  scourer,  (6)  a 
bolting  machine  (reel  separator,  aspirator,  zigzag  separator),  (7)  an 
emery  scouring  machine,  (8)  a  brush  machine,  (9)  a  wetting  apparatus. 
If  the  wheat  is  very  dry,  the  wetting  apparatus  is  to  be  placed  before 

the   emery   scouring    ma- 
chine. 

There  are  two  scourers 
already  in  this  diagram, 
a  rough  and  an  emery 
one.  On  the  first  machine 
the  dirt  sticking  to  the 
grain  is  removed,  and  part 
of  the  germ  coats  and 
beard,  while  the  second 
separates  the  shells  and 
the  remaining  germ  coats 
and  beard.  Each  scourer 
must  be  followed  by  a 
bolting  apparatus,  as  the 
fan  of  the  scourer  leaves 
unextracted  a  certain  per- 
centage of  husks  and 
broken  grain,  and  other 
small  impurities,  which 
FIGt  131.  not  being  sifted  away, 

will   pass   into    the    next 

machine  and  besmear  the  rough  surface  (if  it  be  a  scouring  machine) 
or  dirty  the  grain. 

3.  The  Most  Complete  Type  of  Cleaning. — Beginning  with  a  daily  yield 
of  2000  bushels  and  more,  if  the  milling  is  high,  the  best  style  of  grain 
cleaning  must  be  employed.  It  is  serviceable  to  keep  an  account  of  the 
loss  in  the  grain-cleaning  department,  therefore  automatic  scales  are 
placed  before  and  after  the  cleaning  process.  Fig.  131  gives  a  rough 
diagram  of  the  wheat- cleaning  machinery. 

Out  of  the  storing  bin,  the  grain  is  conveyed  to  automatic  scales  1 
and  then  taken  to  bins  2.  From  the  bin  it  passes  over  the  magnet 


16 


.  m]  FLOUR    MILLING  149 

apparatus  3  to  the  aspirator  4  which  removes  the  large  refuse  to  the  sack 
a,  while  the  dust,  sand,  and  small  matter  are  sent  to  the  sack  b.  In 
this  aspirator  (the  Seek  type,  or  a  zigzag  separator)  the  stock  is  sorted 
into  large  and  small  grain,  the  former  flowing  into  barley  separators  5, 
the  latter  into  cockle  separators  5t.  After  the  barley  separator,  the  grain 
passes  on  (through  a  hopper)  to  re-barley  cylinder  6,  and  the  stock  from 
the  cockle  separator  to  the  re-cockier  6X.  The  grain  cleansed  in 
5-6  and  51-Ql  (small  grain  separated  from  broken  grain  and  cockle)  is 
then  treated  consecutively  on  scourer  7,  in  the  aspirator  8,  in  a  clean 
emery  scouring  machine  9,  aspirator  10,  an  emery  scouring  machine  11, 
aspirator  12  and  a  horizontal  (or  vertical)  brush  machine  13.  After  the 
brush  the  stock  may  be  weighed  on  another  pair  of  scales,  which  will 
inform  us  of  the  loss  in  weight  sustained  in  the  grain-cleaning  department. 
The  scales  are  not  shown  in  the  flow  sheet,  and  the  grain  passes  to  the 
wetting  apparatus  14  here,  whence  it  is  carried  by  conveyor  15  to  be 
tempered  in  bins  16  for  eight  to  twelve  hours.  From  the  bins,  over 
a  magnet  apparatus,  it  is  taken  to  be  ground.  The  capacity  of  the 
bins  must  be  calculated  to  give  a  store  of  grain  for  eight  to  twelve 
hours. 

To  keep  the  scales  and  trieurs  dust  free,  there  is  a  fan  which  exhausts 
the  dust  out  of  the  machine  and  drives  it  to  the  dust-collector.  That 
same  dust- collector  receives  the  dirty  fan-refuse  of  aspirators  4  and  8 
and  rough  scouring  7.  The  dust- collector  passes  the  refuse  to  the  reel 
separator  which  sifts  the  heavy  dust  into  sack  /,  small  refuse  into  //, 
medium  into  ///,  while  the  large  impurities  (chaff,  &c.)  are  tailed  over 
to  IV.  The  broken  grain  and  cockle  separated  by  the  re-cockier  6 
are  then  sorted  in  a  worm  trieur  A,  and  the  former  deposited  in  the  sack 
c,  the  latter  in  the  sack  &..  The  fan-refuse  from  the  finishing  scourers, 
aspirators,  and  brushes  is  sent  to  the  dust-collector  21,  and  thence  to  the 
reel  separator  22  ;  and  the  heavy  refuse  of  the  same  machines  and  the 
throughs  are  discharged  into  sacks  either  in  bulk,  as  shown  in  the  flow 
sheet,  or  the  impurities  from  the  scourers  are  treated  apart  from  the 
throughs  of  the  aspirators  and  the  brush. 

This  flow  sheet  may  be  varied  to  a  large  extent.  If  the  grain  is  very 
hard  and  dry,  the  damping  machine  precedes  the  first  finishing  scouring 
machine  9.  The  aspirator  10  is  often  not  used  even  in  large  mills,  though 
this  tends  to  deteriorate  the  work  of  the  scouring  machine  11.  Very 
rarely  three  emery  passages  are  included  in  the  plan,  besides  the  rough 
scouring  machine,  being  an  unnecessary  luxury.  Sometimes  the  aspirator 
12  is  discarded,  and  only  the  brush  is  retained.  If  the  cleaning  is  to  be 


150 


FLOUR  MILLING 


[CHAP,  ni 


simplified,  the  barley  separator  is  not  included,  and  the  separators  em- 
ployed are  only  the  cockle  separator  and  the  re-cylinder. 

In  well-designed  mills  of  large  capacity  the  large  and  small 
berries  should  not  be  blended  after  passing  the  controlling  trieurs, 
but  cleansed  parallel  on  separate  scourers,  till  they  reach  the 
brush  machines.  The  drystoner  has  to  be  placed  before  the  rough 
scourer  7. 

Grain  Cleaning  in  the  Wet  Scouring  Process. — During  the  period  since 
grain  washing  has  come  into  vogue,  the  cleansing  plan  has  been 

considerably  simplified,  it 

DirtvLrain  being   supposed   that   the 

washing  process  removes 
the  dirt  completely.  Fig. 
132  illustrates  the  clean- 
ing by  washing  system 
recommended  by  Kapler's 
works  (Berlin)  at  the  be- 
ginning of  the  present 
century.  According  to 
this  plan,  from  the  storing 
bin  1  the  grain  is  taken 
to  the  scales  2  and  then 
to  the  separator  3.  The 
screenings  of  the  aspirator 
fan  are  delivered  by  the 
cyclone  4,  the  heavy  im- 
FIG.  132.  purities  to  the  bags  a  and 

6,  the   small  matter  (the 

throughs  of  the  last  sieve)  to  the  bag  c.  The  grain  passes  further  over  a 
magnet  5  to  the  trieurs  6,  whence  the  refuse  is  delivered  to  the  secondary 
trieur,  and  then  washed,  passing  the  stone  separator  8,  the  whizzer  10 
and  the  dryer  12.  The  dryer  is  supplied  with  warm  air  by  the  fan  13 
which  draws  it  out  of  the  heating  chamber  15,  and  the  cold  air  is  impelled 
by  the  fan  14.  Out  of  the  dryer,  the  grain  flows  to  the  scoiiring  machine 
16,  the  brush  machine  17,  and  then  to  the  grinding  machinery.  The 
fan-refuse  collects  in  the  dust-collector  18. 

In  comparing  the  two  plans  we  find  that  the  rough  scourer  and  one 
of  the  finishing  machines  are  left  out  here. 

During  the  last  few  years  in  the  grain  cleaning  with  the  wet  scouring 
or  washing  process  the  rough  scourer  precedes  the  washing.  This  proves 


To  the  bins 


CHAP.   IIIJ 


FLOUR   MILLING 


151 


that  the  washing  of  grain  does  not  answer  its  purpose  as  regards  the 
removal  of  dirt. 

Consequently,  the  modern  wet  scouring  system  of  grain  cleaning  has 
afforded  the  possibility  of  shortening  the  whole  process  by  one  scouring 
passage  only. 

Cheap  water  and  a  steam  motor  make  the  adaptation  of  the  wet 
scouring  system  profitable,  as  the  cost  of  the  water  for  washing  and  the 
comparatively  small  expenditure  of  steam  for  heating  the  air  supplied  to 
the  dryer  are  recovered. 

The  warm  air  is  taken  from  the  heating  chamber,  which  consists  usually 
of  an  iron  riveted  casing  (Fig.  133),  containing  batteries  of  steam  pipes. 
The  steam  is  conducted  to  these  pipes  along  the  upper  external  trunk 


FIG.  133.  FIG.  134. 

furnished  with  a  gauge  showing  the  pressure,  and  let  out  through  the 
lower  tube.  There  are  several  globe  valves  for  regulating  the  steam 
injection- (two,  in  the  present  case),  by  means  of  which  separate  batteries 
of  pipes  may  be  included  or  excluded,  thus  controlling  the  temperature 
of  the  heated  air. 

In  case  a  motor  of  internal  combustion  is  employed  in  the  mill,  the 
heating  chamber  supplying  the  dryers  with  air  cannot  utilise  the  exhaust 
steam.  Special  chambers  with  air-heating  appliances  have  to  be  arranged. 
Fig.  134  shows  a  fairly  simple  chamber  built  of  bricks,  for  that  purpose. 
A  are  the  cast-iron  tubes  down  which  the  products  of  combustion  are 
conveyed  out  on  leaving  the  furnace.  The  burning  in  the  fireplace  B 
is  regulated  by  letting  a  greater  or  less  volume  of  air  into  the  air  blower  a. 
The  exhaust  products  of  combustion  are  ejected  through  s±.  The  cold 
air  streams  into  the  chamber  through  the  inlet  6,  and  is  aspirated  by  a 
fan  through  the  outlet  c. 


152  FLOUR   MILLING  [CHAP,  ill 

However  Simple  this  arrangement  may  be,  still  it  demands  an  extra 
expense  in  fuel.  It  is  desirable,  therefore,  that  the  engineers  should 
utilise  the  exhaust  gases  from  the  motors  of  internal  combustion,  the 
temperature  of  which  often  rises  to  600°. 

Grain  Cleaning  with  Bran  Washing. — The  cleaning  with  bran  in 
Haggenmacher's  machine,  a  process  already  examined,  has  been  very 
lately  adopted  in  Austria-Hungary. 

The  operations  of  those  machines  having  undergone  no  strictly 
scientific  trial  as  yet,  it  is  difficult  to  give  any  definite  opinion,  though 
in  theory,  favourable  results  may  be  expected. 

In  determining  the  place  of  the  bran  "washer"  in  the  flow  sheet  of 
grain  cleaning,  it  must  be  mentioned  that  similarly  to  the  wet  scouring, 
it  ought  to  take  place  of  the  second  scouring  passage.  Yet  it  is  often 
placed  instead  of  the  rough  scourer. 

The  Cleaning  of  Rye. — All  the  flow  sheets  reviewed  contemplate  the 
cleaning  of  wheat.  The  flow  sheet  for  cleaning  rye  is  practically  the 
same,  but  is  curtailed  by  one  scouring  passage.  Yet,  if  the  grist  is 
high,  yielding  up  to  five  kinds  of  flour,  the  usual  three  passages  must  be 
practised,  i.e.  the  plan  in  wheat  cleaning  adhered  to. 


CHAPTER     IV 
GRINDING   THE   GRAIN 

I 

THE  FUNDAMENTAL  PRINCIPLES  OF  MILLING 

ON  leaving  the  grain- cleaning  department,  the  grain  is  sent  to  be  ground 
into  flour. 

Before  proceeding  to  describe  the  grinding  machinery,  the  funda- 
mental principles  of  that  most  important  operation  in  the  industry 
must  be  systematically  considered. 

As  was  shown  in  the  historical  outline  of  flour  milling,  the  primitive 
technics  of  times  gone  by  produced  but  two  principles  of  reducing 
the  grain — impact  and  friction ;  and  the  materials  of  which  the 
milling  implements  were  made  were  almost  exclusively  natural  stones. 
In  this  primitive  process  both  the  grain  and  offals  were  ground. 
The  necessity  of  removing  the  non-nutritive  bran,  however,  considerably 
modified  the  system  by  evoking  new  principles  of  trituration,  while 
new  materials  for  the  working  organs  of  the  machinery  afforded  the 
possibility  of  putting  those  principles  into  practice. 

In  classifying  the  types  of  milling  machinery  existing  in  modern 
technics,  according  to  the  principles  of  action  of  their  working  organs 
upon  the  product  under  treatment,  the  machines  must  be  divided  into 
the  three  following  categories  : 

(1)  Cutting  (chipping  off )  machines. 

(2)  Pressing  (crushing)  machines. 

(3)  Machines  acting  by  free  impact. 

The  machinery  of  the  first  principle  of  reduction  requires  two  work- 
ing parts  moving  in  opposite  directions,  or  in  the  same  but  with  different 
speeds  (Fig.  135).  It  is  evident  that  the  working  surfaces  A  and  B  in 
these  machines  should  be  sharp  and  rough. 

The  second  principle  of  action  of  the  working  parts  upon  the  pro- 
duct treated  is  never  met  with  in  its  pure  form,  because  those  parts 
move  with  a  velocity  different  to  that  of  the  product,  and  the  grain, 

153 


154 


FLOUR   MILLING 


[CHAP.   IV 


besides  being  crushed,  loses  particles  that  are  chipped  off  not  by  the 
strain  of  the  cutting  facets,  but  through  friction.  This  process  is  called 
triturating  the  product.  In  this  case,  too,  the  working  parts  may  be 
moving  either  in  different  or  in  one  and  the  same  direction.  If  running 
in  the  latter  manner,  their  speeds  must  be  different.  An  immovable 
position  of  one  of  the  working  surfaces,  as  in  millstone  sets  for  instance, 
is  also  possible.  In  Fig.  136  we  have  a  diagram  of  the  treatment  the 
product  receives  according  to  the  second  principle.  The  direction  of 
movement  of  the  working  surfaces  is  marked  by  arrows  s,  the  pressing 
force  by  N.  Then  the  forces  of  friction  are  Nf,  f  being  the  coefficient  of 
friction  of  the  product  against  the  working  surface.  The  breaking  down 


FIG.  136. 


of  the  grain  or  of  a  part  of  it  will  be  effected  in  planes  parallel  to  the 
acting  powers.  The  working  surfaces  A  and  B  may  be  smooth  in  that 
case,  but  with  a  high  coefficient  of  friction  /. 

The  third  and  last  principle  of  reduction,  the  free  impact,  gives  us 
machinery  the  working  parts  of  which  by  striking  impart  a  great  kinetic 

(  IYY\  ?/    I 

energy  to  the  grain,  which  destroys  it.     In  these  machines  the 

speed  of  motion  of  the  working  organs  must  be  very  great,  for  the  mass 
of  grain  m  is  insignificant. 

The  aim  of  the  machines  of  the  first  principle  of  treatment  is  to 
produce,  by  a  consecutive  series  of  cutting,  particles  (middlings)  contain- 
ing bran  and  free  of  it. 

In   the   milling   process   to   follow,    we   shall   separate   the   branny 


CHAP,  iv]  FLOUR   MILLING  155 

middlings  from  the  starchy  semolina  and  then  proceed  to  reduce  it 
to  flour. 

If  the  machine  is  to  fulfil  its  purpose  successfully,  the  working  sur- 
faces, as  mentioned  before,  must  be  sharp  and  rough.  Hard  natural 
and  artificial  stones,  coarse-grained  and  porous,  are  a  good  material  for 
surfaces  of  this  kind  ;  as  well  as  metals  which  are  easily  shaped  to 
the  desired  form  of  a  surface  with  sharp  cutting  edges,  and  hardened 
to  a  necessary  degree,  and  thus  able  to  stand  a  lengthy  period  of 
work. 

When  the  stock  is  broken  down  to  semolina  on  machinery  of  the  first 
type,  we  proceed  to  reduce  it  to  flour.  This  is  performed  by  machines 
working  on  the  second  principle  of  treatment.  The  power  of  friction 
plays  a  part  in  such  machinery,  the  working  surfaces  with  a  large 
coefficient  of  friction  may  be  fashioned  of  fine-grained  natural  stone, 
artificial  stone  (emery,  porcelain,  &c.),  or  dull  cast  iron. 

For  machinery  working  on  the  third  principle,  ^only  metal  is  used, 
this  being  the  most  durable  material. 


II 

THE  CONSTRUCTION  OF  THE  GRINDING  MACHINES 

As  we  have  seen,  the  form  of  the  working  parts  of  the  grinding 
machinery  is  defined  either  in  the  shape  of  chisels  (Fig.  135),  or  that  of 
a  part  of  the  surface  (Fig.  136)  with  a  large  coefficient  of  friction  in 
respect  to  the  grain.  If  a  mass  of  whole  grain  or  particles  is  to  be 
triturated  unintermittently,  the  chisels  are  arranged  one  after  the  other, 
thus  forming  a  surface  covered  by  uniformly  placed  chisels.  Conse- 
quently, speaking  of  the  working  organs  in  machinery  of  the  first  and 
second  principles,  we  have  the  right  to  name  those  parts  surfaces.  The 
working  organs  of  the  machinery  based  on  the  third  principle  present 
separate  elements  adapted  for  striking,  generally  metal  pins. 

Applying  the  same  considerations  that  guided  us  in  our  choice  of 
the  form  of  working  organs  for  scouring  machines,  here  we  select  two 
kinds  of  working  surfaces,  cylindrical  and  flat. 

There  being  two  working  surfaces  necessary  for  treating  the  product, 
a  question  arises  concerning  the  degree  of  their  activity.  There  are  two 
possibilities  :  ( 1 )  one  of  the  working  surfaces  is  fixed,  the  other  movable ; 
(2)  both  are  movable. 

As  regards  the  arrangement  of  the  surfaces,  there  can  also  be  two 


156  FLOUR   MILLING  [cHAt.  IV 

cases  :  (1)  working  surfaces  having  a  common  axis  of  rotation,  and 
(2)  surfaces  with  parallel  axes  of  rotation. 

The  period  spent  by  the  grain  between  the  working  surfaces  is  of 
the  greatest  consequence,  because  the  degree  of  uniformity  of  the  tri- 
turated particles  depends  on  it.  In  this  respect  the  working  surfaces 
are  divided  into  two  categories  :  (1)  surfaces  of  reiterated  action,  and 
(2)  surfaces  acting  once.  In  the  first  case  we  have  mostly  to  do  with 
planes  between  which  the  product  is  treated ;  in  the  second,  with  cylindric 
surfaces  where  the  working  organs  come  into  contact  along  a  line. 

To  the  category  of  machines  with  reiterated  action  of  the  working 
surfaces  pertain  millstones,  desintegrators,  &c..  i.e.  machinery  having 
a  common  axis  of  rotation  ;  to  the  second,  roller  mills,  i.e.  machines 
with  parallel  axes  of  rotation  of  the  working  surfaces.  This  order  is 
established  by  the  historic  consecutiveness  in  the  development  of  flour- 
milling  technics  and  by  the  degree  of  perfection  of  the  two  types  of 
machinery.  For  this  reason  we  shall  study  the  machines  in  the  order 
of  their  technical  perfection. 


Ill 

MACHINES  OF  REITERATED  ACTION  OF  THE  WORKING  SURFACES 

Millstone  Sets  (burrs). — Before  passing  to  millstones,  it  is  necessary 
to  prove  that  other  working  surfaces  of  reiterated  action  besides  planes 
are  inadaptable  from  the  point  of  view  of  the  principles  we  have  stated, 
as  well  as  constructively. 

As  the  machinery  of  reiterated  action  of  the  working  surfaces  must 
have  a  common  axis  of  rotation,  the  following  combinations  are  possible 
here  :  (1)  cylindric  surfaces  inscribed  one  in  another,  (2)  similarly  in- 
scribed conic  surfaces,  and  (3)  parallel  planes. 

In  all  three  cases  the  axis  may  be  vertical  or  horizontal. 

To  begin  with,  the  combination  with  a  vertical  axis  of  rotation 
must  be  discarded  in  the  first  two  cases,  for  under  such  conditions  the 
time  spent  by  the  stock  between  the  working  surfaces  is  shortened, 
because,  influenced  by  its  proper  gravity,  the  stock  passes  between  the 
two  working  surfaces  more  rapidly,  and  consequently  requires  surfaces 
of  large  dimensions,  which  makes  the  machine  more  expensive.  Further, 
the  combination  of  cylindric  surfaces  with  a  horizontal  axis  of  rotation 
must  also  be  rejected,  because  the  wear  of  the  working  surfaces  makes 
it  impossible  to  keep  them  within  the  desired  distance  of  each  other,  a 


CHAP,  iv]  FLOUR   MILLING  157 

consideration  in  regard  to  its  construction  which  also  applies  to  the 
preceding  cases.  Conic  surfaces  with  horizontal  or  vertical  axes  of 
rotation,  though  affording  the  possibility  of  bringing  them  closer  to  each 
other  in  proportion  to  their  wear,  have  different  peripheral  velocities  of 
revolution,  and  consequently  exclude  equability  in  the  treatment  of  the 
product  and  in  the  wear. 

Thus  only  machinery  with  flat  working  surfaces,  having  either  a 
horizontal  or  vertical  axis  of  rotation,  remains. 

In  machinery  of  this  type  the  following  combinations  of  rotation  are 
possible  :  if  the  axis  is  vertical,  (a)  either  the  upper  working  surface 
revolves,  while  the  bottom  one  is  stationary;  or  vice  versa,  and  (b)  both 
the  surfaces  rotate  in  opposite  directions.  The  same  may  be  said  of 
the  horizontal  axis — either  one  only  or  both  the  working  surfaces  may 
be  rotating. 

Coming  to  constructive  descriptions  and  a  critical  consideration  of 
the  existing  types  of  stone  mills,  it  must  be  mentioned  in  the  first  place 
that  the  working  organs  of  that  machine,  the  grinding  stones,  are  shaped 
of  hard  natural  rock  or  artificial  stones,  as  well  as  of  metal  (steel,  cast 
iron).  We  shall  give  a  detailed  description  of  these  materials  later,  and 
proceed  now  to  describe  stone  mills  with  a  vertical  axis  of  rotation. 

1.  Stone  Mitts — Horizontal  (Vertical  Axis  of  Rotation) 

Stone  mills  with  a  vertical  axis  of  rotation  are  divided  according  to 
construction  into  three  types,  viz.  : 

(1)  Stone  mills  with  a  rotating  upper  stone, 

(2)  Stone  mills  with  a  rotating  bottom  stone, 

(3)  Stone  mills  with  both  the  upper  and  bottom  stones  rotating. 
The  simplest  type  of  a  burr  mill  having  a  rotating  upper  stone  is 

shown  in  Fig.  137.  The  upper  rotating  stone  B,  the  runner,  is  set  on 
a  vertical  shaft  iji  by  means  of  a  cross-head  g,  the  driving  iron.  The 
shaft  i  is  called  a  spindle  and  is  brought  into  rotation  by  a  pulley  F, 
or  a  gear  drive.  The  lower  part  i  of  the  spindle  ends  in  a  pivot- journal  p 
resting  on  a  step-bearing  t°,  while  its  upper  part  il  is  held  in  a  vertical 
bearing  k,  the  mill-bush,  and  is  connected  with  the  cross-head  through 
an  octagonal  truncated  pyramid  h.  Often  for  simplicity's  sake  the  end 
of  the  spindle  is  shaped  to  a  square  section.  The  bottom  stone  (7,  the 
fixed  bedstone,  is  set  in  a  frame  /.  The  vertical  bearing  k  is  set  in  a 
cup  r  cast  in  one  piece  with  the  frame  7.  To  prevent  the  grain  from 
falling  through  the  aperture  o-o  of  the  bedstone  c,  this  aperture  is  covered 


158 


FLOUR   MILLING 


[CHAP,  iv 


over  by  a  plank  l-L  The  distance  between  the  grinding  surfaces  B 
and  C  is  adjusted  by  a  cone  and  worm-drive  in  the  following  manner  ; 
the  vertical  axle  t  ending  in  a  hub  with  a  square  hole,  is  set  upon  the 
square  end  ^  of  the  axle  n  and  rotates  driven  by  hand-wheel  s.  The 
axle  w  which  sets  the  worm  wheel  x  into  motion  is  turned  by  a  cone- 
drive  u-r.  The  screw  y  with  a  square  thread  ending  in  a  plug  m  rises 
or  falls,  lifting  or  lowering  the  cup  z,  in  which  the  step-bearing  t°  is  set. 
The  spindle,  and  with  it  the  top  stone  B,  is  lifted  or  lowered  together 

with  the  step-bearing. 

Out  of  the  hopper  a, 
the  grain  flows  through 
nozzle  b  and  tube  c  into 
the  feeding  tube  e  and 
falls  on  the  table  /  which 
is  fixed  to  the  cross-head, 
and  gyrating  together 
with  it,  flings  the  grain 
into  the  grinding  zone,  as 
indicated  by  arrows. 
The  feeding  tube  e  is 
raised  or  lowered  by 
levers  d,  which,  with  the 
cup  g  and  the  screw  hub 
gl  form  one  block,  owing 
to  which  the  flow  of 
grain  is  regulated,  for 
the  cross  section  of  the 
outflowing  stream  of  grain 
diminishes  or  increases. 

The  millstones  are  en- 
closed in  a  timber  cylindric  casing  M  carrying  on  its  upper  lid  a  cross- 
head  Q  with  a  hub  for  the  feeding  tube  e.  The  reduced  product, 
collecting  between  the  grinding  stone  and  the  casing,  is  shifted  by 
scrapers  Sj_  to  the  outlet  spout  G  and  descends  to  the  elevator  H  or 
directly  into  bags.  At  the  head  of  the  spout  G  there  is  an  opening  6, 
usually  covered  with  a  lid,  through  which  the  product  may  be  sampled. 

The  stone  mill  is  mounted  on  a  bursting  supported  by  cast-iron 
columns  or  timber  stands,  while  the  frame  of  the  step-bearing  rests  on  a 
special  foundation  R.  In  mills  the  sets  of  grinding  stones  are  oftep 
planted  on  the  bottom  of  the  second  floor. 


FIG.  137. 


159 


CHAP,  iv]  FLOUR    MILLING 

Fig.  138  shows  a  millstone  plant  of  the  portable  type  driven  by 
a  toothed  gearing.  The  hand-wheel  of  the  mechanism  adjusting  the 
distance  between  the  grinding  surfaces  here  is  placed  below,  and  the 
feed  is  regulated  by  a  lever  appliance  raising  or  lowering  the  feed-tube. 
On  the  frame  is  set  a  simplified  crane  for 'lifting  the  grinding  stones. 

From  the  description  of  a  characteristic  design  of  a  stone  mill  we 
gather  that  the  fundamental  parts  of  this  machine  are  firstly  its  working 


FIG.  138. 

organs,  i.e.  the  grinding  stones,  and  secondly,  the  auxiliary  mechanisms 
setting  the  stones  and  regulating^their  work. 

In  the  design  examined  one  important  detail  is  missing,  the  appliance 
.for  aspirating  the  machine.  It  is  a  known  fact  that  a  considerable 
amount  of  the  work  of  friction  is  transformed  to  heat.  Owing  to  this, 
the  product  treated  between  the  stones  becomes  excessively  heated, 
which  is  detrimental  to  the  quality  of  the  flour. 

Fig.  139  represents  G.  Luther's  construction  of  stone  mills  with 
dust-collectors.  Between  the  cap  of  the  casing  and  the  top  stone  there 
is  a  dust-collector  A,  a  fan-like  circle  covered  with  a  dust-proof  cloth 


160 


FLOUR   MILLING 


[CHAP,  iv 


—linen,  generally.  The  dust-collector  is  suspended  to  the  cap  of  the 
casing  of  the  same  kind  of  cloth  B.  A  trunk  C  communicating  with 
the  fan,  is  let  into  the  dust- collecting  chamber.  The  pulleys  b  and 
a  drive  the  mechanism  which  shakes  the  dust- collector ;  this  consists 
of  a  worm  and  cross-head  gearing  to  the  rod  t  which  is  connected  with 
the  dust-collector.  The  frame  of  the  dust- collector  being  of  a  strong 
system,  the  part  of  the  dust- collector  opposite  to  the  rod  t  receives 
the  shocks  of  the  shaking  action  and  returns  them  by  the  spring  r.  The 
air  streams  in  as  indicated  by  arrows  s,  passes  between  the  grinding 
stones,  and  is  exhausted  (s^)  through  the  dust-collector,  carrying  the 
dust  with  it.  The  air  and  grain  passage  is  isolated  from  the  casing 
chamber  likewise  by  cloth  sleeve  or  a  timber  spout. 

Fig.  140  is  a  dust-collector  for  a  stone  mill  from  A.  Wetzig's  works,  with 


FIG.  139 


FIG.  140. 


a  shaking  appliance.  We  see  here  that,  during  the  shaking  motion,  the 
aspirating  tube  A  is  closed  by  the  valve  b  with  a  rod  a,  otherwise,  if  the 
apparatus  were  shaken  while  aspirated,  the  particles  of  dust  would  not 
be  thrown  off  the  dust-collector,  because  they  would  be  pressed  against 
it  by  the  aspirated  air. 

Having  become  acquainted  with  the  type  of  the  machine,  we  shall 
proceed  now  to  the  details  of  the  stone  mills. 


2.  Composition  and  Design  of  Millstones 

Grinders  of  Natural  Stone. — Before  the  technics  produced  any  satis- 
factory results  in  the  preparation  of  artificial  stones,  the  grinders  were 
shaped  of  solid  rock,  and  the  materials  used  were  :  (A)  quartz  stones,  (B) 
porphyritic  and  granite,  (C)  sandstones,  and  (D)  stones  of  volcanic  origin. 

When  selecting  the  kind  of  stones  their  properties  must  be  taken 


CHAP,  iv]  FLOUR    MILLING  161 

into  account,  in  order  to  guarantee  a  high  standard  of  work  and  impart 
a  durability  to  the  grinders.  Therefore,  the  quality  of  the  natural 
stones  may  be  determined  by  the  following  properties  : 

(1)  The  hardness  of  the  stone  is  the  greatest  guarantee  of  a  lengthy 
period  of  service,  and  consequently,  the  hard  kinds  are  to  be  preferred, 
if  the  other  qualities  of  the  stones  are  equal. 

(2)  Tenacity. — If  the  hard  stones  crumble  very  much  when  struck, 
they  cannot  be  used  as  millstones.     It  is  indispensable  that  the  stone 
should  be  of  a  sufficient  toughness,  making  all  crumbling  impossible. 

(3)  Porousness. — Stones  apt  to  become  polished  must  be  avoided. 
This  is  possible  if  the  stone  is  of  porous  structure.     Those  stones  are  to 
be  considered  best,  which  are  granulous  in  structure,  on  which  the  porous- 
ness depends.    In  such  a  case,  when  the  upper  coat  of  the  stone  is  worn  off 
by  work,  it  lays  bare  a  fresh  surface  just  as  rough  as  the  one  rubbed  off. 

(4)  Uniformity    of    Structure.  — Uniform    work    is    obtained    only 
when  the  coating  of  stone  worn  off  is  supplanted  by  another  of  equal 
structure.     For  this  reason  the  structural  uniformity  of  the  stone  is  of 
great  importance. 

(A)  Quartzose  Stones. — The  best  kind  of  quart zose  stones,  satisfactory 
in  all  the  above-mentioned  respects,  are  the  French  stones  with  a  fame 
of  200  years  standing,  procured  in  the  vicinity  of  La  Ferte-sous-Jouare 
in  the  Department  of  the  Seine.     Geological  investigations  prove  that 
this  locality  used  to  be  a  bay  at  some  epoch,  into  which  a  large  river 
flowed.     The  formation  of  a  quartzose  or  silicious  incrustation  leads  us  to 
suppose  the  existence  of  many  hot  springs  there  at  the  time,  spouting 
water  rich  with  silicic  acid  or  silica. 

The  real  French  stone  from  La  Ferte  is  of  a  beautiful  roseate  hue. 

Another  bed  of  quartzose  stones  in  France  lies  in  Bergerac.  But 
these  stones  are  less  porous.  They  are  almost  perfectly  white. 

In  some  parts  of  Hungary  also  there  are  beds  of  stones,  closely  ap- 
proaching those  of  La  Ferte  in  their  qualities. 

In  Russia  quartzose  stones  of  a  fair  quality  are  to  be  found  close  to 
station  Suleya  of  the  Samara-Zlatoust  railroad,  gov.  of  Uffa,  stone 
quarry  of  N.  Lazareff.  Possessing  the  fine  toughness,  porousness,  and 
uniformity  of  the  French  stones,  they  are  considerably  inferior  to  them 
in  hardness. 

(B)  Porphyry  and  Granite  Stones. — These  very  hard  stones  are  gene- 
rally not  porous,  and  become  rapidly  polished  from  work.     The  best 
kinds  of  porphyry  and  granite  for  making  grindstones  are  obtained  in 
Germany  near  Cravincler,  and  in  Austria  close  to  Perg  on  the  Danube. 


162  FLOUR   MILLING  [CHAP,  iv 

(C)  Sandstones. — Grinders  of  sandstone  strata  are  used  almost  ex- 
clusively on  simple  farm  mills.     Sandstones  consist  of  fine  quartz  crystals, 
and  consequently  reduce  the  integument  of  the  grain  very  much.     In 
addition,  being  of  an  insufficient  toughness,  these  stones  easily  crumble, 
leaving  small  particles  of  quartzose  crystals  in  the  meal. 

The  sandstone  quarries  lying  in  the  valley  of  the  Oka  near  Moscow, 
and  in  the  Dnieper  valley  by  Poutivl,  are  considered  to  be  the  best  in 
Russia. 

(D)  Stones  of  Volcanic  Origin. — In  respect  to  their  quality  the  stones 
of  volcanic  origin  closely  approach  the  French  quartzose  stones.     Before 
the  discovery  of  the  La  Ferte  stones,  they  were  the  best. 

The  best  known  localities  are  the  volcanic  stone  quarries  along  the 
Rhine  in  Germany  (Andernach).  The  quarries  yield  hardened  lava  of 
basalt  (the  stones  are  called  Lavastein),  very  hard,  tough,  and  porous, 
grey  in  colour. 

In  some  parts  of  Hungary  (Bars  Geletnek)  trachyte  stones  are  obtained 
of  a  high  quality,  and  in  Italy  the  lava  from  Mount  Etna  gives  good  grey 
basalt  stones. 

Grinders  of  Artificial  Stone. — The  difficulty  of  procuring  good  natural 
stones,  their  comparative  expensiveness  and  variety  in  structure,  com- 
pelled manufacturers  as  far  back  as  thirty  years  ago  to  begin  making 
artificial  grinding  stones.  It  is  comparatively  but  quite  lately,  that  the 
attempts  have  been  crowned  with  success,  but  now  the  miller  is  in  posses- 
sion of  more  or  less  perfect  artificial  stones  for  milling  purposes. 

The  problem  of  producing  artificial  grinders  may  be  regarded  as 
solved  when  a  hard  rock  reduced  to  particles  is  so  firmly  cemented 
together,  as  to  form  a  stone  possessing  all  the  qualities  of  natural  stones. 

The  principal  materials  used  in  making  artificial  stones  are  quartz, 
silex,  emery,  corundum,  carborundum,  and  electrite,  very  hard  rocks.  The 
cementing  materials  employed  are  :  magnesite  (MgO — oxide  of  mag- 
nesium), magnesium  chloride  (MgCl2),  field  or  river  spar,  glass  solution, 
muriatic,  and  several  other  acids. 

In  accordance  with  the  purpose  of  the  grinder,  the  hard  stone  is  broken 
to  small  pieces  beginning  with  the  size  of  a  wheat  berry  and  ending  in 
particles  of  the  size  of  coarse  sand.  Generally  there  are  five  kinds  of 
gravel  prepared,  viz.  No.  1,  the  largest,  used  for  grinding  oats  (seldom 
used)  and  No.  5,  the  finest,  used  for  grinding  stones  in  millet-scouring 
machines.  Grinders  for  milling  rye  and  wheat  are  prepared  of  the  inter- 
mediate Nos.  (2,  3,  4)  of  gravel. 

The  gravel  used  is  either  of  one  kind  of  stone,  or  a  mixture  of  two  kinds, 


CHAP,  iv]  FLOUR   MILLING  163 

of  equal  hardness.     The  approximate  composition  of  artificial  stone  is 
as  follows : 

Hard  stone  (quartz,  emery,  &c.)    .         .         .         .70  per  cent. 

Magnesite  (MgO)   .         .        .        .        .         .         .     16 

Solution  of  magnesium  chloride     ,     .   .         .         .14        ,, 

Total       .        .       \        .        ,         .        .  100 

The  magnesite  must  be  perfectly  pure,  unmixed  with  any  other  salts 
or  oxides.  The  magnesium  chloride  is  taken  in  water  solution  35°  to  37° 
strong  according  to  Bomet's  areometer. 

At  the  present  time  in  Russia  there  are  a  good  many  works  in  which 
artificial  millstones  are  made  by  hand,  and  the  composition  of  the 
stones,  or  of  the  surfaces  in  emery  scourers,  is  determined  according  to 
various  recipes.  But  there  are  few  well-equipped  works.  The  best  are 
in  Petrograd,  e.g.  the  works  of  N.  Strook ;  in  Samara,  "  The  First  Grind- 
stone Works  "  ; l  and  in  Riga,  "  The  Economical  Trading  Co." 

The  best  artificial  millstone  factories  import  quartzose  stone  in  pieces 
from  France  (La  Ferte-sous-Jouare)  which  contains  the  highest  percentage 
of  oxide  of  silicium  (Si02)  ;  silex  having  the  least  percentage  of  chalk 
(CaCo3)  from  Denmark  ;  emery,  with  the  highest  percentage  of  corund 
(A1203)  from  Naxos.  The  gravel  is  prepared  by  the  makers  on  special 
stone-crushing  machinery.  The  hand- workers  generally  get  ready-made 
gravel  chiefly  from  French  or  German  works. 

Metal  Millstones. — The  attempts  to  substitute  metal  grinders  for 
stone  ones  date  from  equally  remote  times.  Much  has  been  done  in  that 
respect  by  the  Americans,  who  have  obtained  good  results  in  the  end. 

In  Russia  machines  with  metal  grinding  stones  are  not  widely  used, 
whereas  in  America  they  are  very  much  in  use  for  grinding  maize,  barley, 
oats,  &c.,  to  a  meal. 

The  material  employed  for  making  metal  grinders  is  hardened  cast 
iron  and  hard  steel.  The  impossibility  of  renewing  the  working  surface 
once  it  is  worn  off,  is  a  great  disadvantage.  This  defect,  however,  is 
obviated  now,  by  making  the  grinding  surface  removable  and  thin. 
Thus  the  worn  grinding  disc  is  thrown  away  and  is  replaced  by  a  new 
one,  which  incurs  no  great  expense. 

\/The  Construction  of  Stone  Grinders. — The  normal  construction  of 
grinders  for  upper  runner  mills  was  evolved  by  French  works  and  almost 
universally  accepted.  The  outline  of  the  working  surfaces  of  the  upper 
and  lower  stones  constitutes  an  essential  part  in  their  construction, 

i  See  Russian  MiUer,  1912,  No.  1. 


164 


FLOUR   MILLING 


[CHAP,  iv 


Fig.  141  gives  us  a  rough  sketch  of  the  upper  and  the  lower  stones.  We 
see  in  this  sketch  that  the  grinding  surfaces  of  both  the  stones  are  not 
flat.  The  opening  A  in  the  upper  runner  is  named  the  eye  ;  the  zone  B 
between  points  1  and  2  is  called  the  heart ;  C,  between  2  and  3,  the  inter- 
mediate zone  ;  D,  from  3  to  4,  the  reducing  zone  ;  E,  4  to  5,  the  grinding 
zone.  In  this  way,  the  surface  of  the  stone  between  points  1  and  4  is 
curved,  while  its  grinding  part  proper,  between  points  4  and  5,  is  a  plane. 

The  loophole  F  in  the 
bed  stone  serves  for  passing 
the  spindle  through  it  and 
setting  the  vertical  step- 
bearing.  The  surface  of  the 
bottom  stone  from  the  point 
&,  corresponding  to  point  4 
of  the  runner,  is  chiselled  to 
the  shape  of  a  cone  up  to 
point  a. 

The  outline  of  the  work- 
ing surfaces  given  here  was 
developed  by  French  works 
and  accepted  almost  every- 
where. In  Russia,  the  name 
"  grinding  zone  "  or  "  slide  "  is  applied  to  D  and  E,  while  the  intermediate 
region  C  is  called  the  region  of  full  contact.  The  surface  B  and  C  is  named 
in  Russia  the  "  swallow."  The  dimensions  characterising  the  mill- 
stones of  the  examined  normal  type,  are  given  in  the  following  table, 
where  h  denominates  the  depth  of  the  swallow  in  the  top  stone,  and  hl  in 
the  bed  stone. 

TABLE    XVI 


FIG.  141. 


Diameter  of 

Top  Stone. 

Bed  Stone. 

2R. 

H. 

h. 

A. 

B+C. 

D+E. 

fl"i-       - 

At. 

mt. 

cm. 

mm. 

cm. 

cm. 

cm. 

cm. 

mm. 

1-1-6 

30-50 

2-3J 

25-40 

20-30 

15-25 

15-25 

1-1J 

In  Russia  the  stones  are  usually  measured  in  quarters  of  an  arshin, 
and  according  to  the  number  of  quarters  in  the  diameter  are  called 
"  quartuple,"  "  quintuple,"  &c.  The  largest  sized  Russian  stone  is 
the  "  octuple,"  56-inch  diameter. 


CHAP.   IV 


FLOUR    MILLING 


165 


FIG.  142. 


The  working  surfaces  of  the  upper  and  the  lower  stones  form  a  common 
swallow  a  which  catches  the  grain,  crushes  it,  pushes  it  to  point  3, 
and  grinds  it  to  meal  on  its  way  from  3  to  4. 

The  general  view  of  the  working  surfaces  of  the  grinders  is  shown 
in  Fig.  142.  A  is  the  bed  stone,  and  .B  is  the  upper  rotating  stone. 

For  the  sake  of  durability 
the  stones  are  encircled  with 
hoops  (generally  two)  set  on 
when  hot.  This  is  particu- 
larly important  for  the  run- 
ner, which  develops  a  great 
centrifugal  force,  while  re- 
volving, and  may  be  torn  to 
pieces  if  the  stone  is  too 
friable,  a  and  6,  parts  of 
the  swallow,  are  made  of 
firm  concrete.  The  circles  A  and  B  (part  of  C,  D,  and  E),  the  working 
parts,  are  of  natural  or  artificial  rock. 

On  the  upper,  as  well  as  on  the  lower  stone,  there  are  furrows,  which 
if  one  stone  is  laid  upon  the  other,  cross  each  other  at  an  angle.  The 
purpose  of  these  furrows  is  the  following  :  firstly,  the  sharp  edges  of  the 
furrows  are  supposed  to  cut  the  grain  ;  secondly,  by  means  of  these  fur- 
rows the  working  space  is 
ventilated.  As  concerns 
the  first  supposition,  it 
cannot  be  regarded  as  cor- 
rect, for  the  cutting  action 
is  performed  by  the  crys- 
tals of  the  stone  itself. 
The  edge  of  the  furrow 
then,  is  so  rudely  outlined, 
owing  to  the  porousness 
of  the  stone,  that  there  can  be  no  idea  of  cutting,  not  to  mention  the 
fact  that  the  cutting  angles  of  the  edges  are  too  large,  which  is  notice- 
able in  the  various  forms  of  cross-section  of  the  furrows  (Fig.  143). 

Of  these  forms  of  furrows  the  one  marked  V  is  the  most  preferable, 
because  the  product  broken  into  large  pieces  is  more  easily  picked  out  of 
the  cavity  of  the  under  furrow  by  the  edge  of  the  top  one,  and  may  then  be 
subjected  to  a  further  reduction.  It  is  followed  by  shape  IV,  which  may 
be  had  in  two  variations,  viz.  with  the  angle  k  and  without  it,  when  the 


FIG.  143. 


166  FLOUR   MILLING  [CHAP,  iv 

bottom  of  the  furrow  cd  is  continued  to  the  surface  of  the  millstone, 
i.e.  has  the  plane  of  cd±  and  ajb.  But  this  furrow  is  worse  than  the  Vth 
one,  for  there  will  be  more  product  collected  in  the  angle  c  and  the  diffi- 
culty of  driving  it  out  will  increase. 

The  bottom  ab  of  the  furrow  V  lies  on  a  curved  plane,  but  is  usually 
made  flat.  The  difference  between  the  Vth  form  and  the  second  varia- 
tion (bottom  cdi)  of  the  I  Vth  one  lies  in  the  fact  that  the  angle  c  in  the 
I  Vth  form  is  acute,  while  the  corresponding  angle  a  of  variation  V  is 
obtuse. 

The  dimensions  of  the  cross  section  of  these  furrows  are  the  following  : 
depth  h  =  9  to  13  mm.  ;  breadth  c&=30  to  35  mm. 

It  is  evident  from  the  second  position  of  the  furrows  in  variation  F, 
that  the  grain  or  a  particle  of  it,  A,  is  chipped  in  the  plane  xy,  when  the 
planes  of  the  furrows  approach  each  other  during  the  rotation  of  one 

of  the  stones,  and  the  chipping  forces 
are  Nf,  where  /  is  the  coefficient  of 
friction. 

As  to  the  furrows  formed,  as  shown 
in  /,  //,  and  ///,  they  are  scarcely  ever 
used  in  practice,  being  disadvantageous 
in  all  respects. 

To  arrive  at  a  clear  understanding 
of  the  significance  of  differently  out- 
lined forms  of  the  furrows,  it  is  necessary  to  become  acquainted  with  the 
theory  of  their  functions. 

It  is  supposed  that  the  furrows  act  upon  the  product  under  treatment, 
as  a  cutting  organ  and  scraper  which  propel  the  grist  to  its  exit. 

Let  us  examine  the  propelling  action  of  the  furrows,  taking  for 
granted  that  we  have  the  most  common  outline  of  furrows,  i.e.  curved. 
ab  (Fig.  144)  is  a  furrow  of  the  upper  rotating  stone,  cd  that  of  the  lower 
one.  Between  them  at  the  point  m  there  is  a  particle  of  product. 
Through  m  to  the  furrows  are  drawn  tangents  t  and  tlt  which  form  an 
angle  a,  called  the  angle  of  inclination  of  the  furrows.  The  pressure  upon 
the  product  in  the  furrows  cd  and  ab  we  denominate  through  p  and  p± ; 
/  is  the  coefficient  of  friction.  The  propelling  of  the  product  along  ab  to 
its  exit  is  possible  if  the  sum  of  the  projections  of  all  forces  acting  upon  m 
on  the  tangent  tl  exceeds  zero,  i.e.  : 

p1  sin  a—fp1  cos  a—fp>  0. 
There  being  no  movement  of  the  product  in  the  direction  perpen- 


CHAP,  iv]  FLOUR   MILLING  167 

dicular  to  t,  the  total  of  the  projections  of  all  forces  acting  in  this  direction 
must  be  equal  to  zero : 

p—pi  cos  a—fpi  sin  a=0. 

By  placing  the  signification  of  P=PI  cos  a+fp1  sin  a  in  the  preceding 
inequality  and  performing  the  corresponding  alterations,  we  obtain  : 


Sin  a  (1—  /2)>  2/cos  a,  or  tg  a> 


2f 
_J 


or  a> 


because  f=tg  <p.  Thus,  for  the  particle  m  to  travel  along  ab,  it  is  neces- 
sary that  the  angle  of  inclination  of  the  furrows  should  be  greater  than  the 
double  angle  of  friction.  And  to  keep  the  propelling  forces  even,  the 
furrows  must  be  necessarily  kept  at  an  even  angle  of  inclination. 

The  Outline  of  the  Furrows.  —  In  Fig.  142  representing  French  mill- 
stones, we  have  seen  the  most  common  and  widespread  form  of  outline  of 


II 


III 
FIG.  145. 


IV 


V 


the  furrows.  But  besides  this  outline,  there  exist  several  others.  The 
most  important  ones  are  shown  on  Fig.  145. 

Here  the  furrows  marked  ///  are  built  in  a  logarithmic  curve,  //  are 
rectilinear  furrows  (the  main  a,  and  the  intermediate  b  and  c  have  one  and 
the  same  degree  of  eccentricity  07,  the  size  of  which  is  equal  to  one-sixth 
to  one-third  of  the  radius  of  the  millstone),  IV  are  Evans'  furrows,  and 
F,  lastly,  the  novel  circular  furrows. 

The  outline  of  the  rectilinear  furrows  of  both  types  is  very  simple. 
That  of  the  furrows  drawn  in  curves  is  more  complicated. 

The  different  outlines  of  the  curved  furrows  are  supported  by  the 
theory  of  the  movement  of  the  product  mentioned  above.  From  the 
point  of  view  of  this  theory,  the  logarithmic  curve  furrows  are  ideal, 
their  angle  of  inclination  being  constant.  We,  however,  absolutely  pro- 
test against  this  theory,  holding  it  to  be  wrong  at  its  very  root. 

First  of  all,  we  know  that  the  character  of  the  working  surfaces  of  the 
grinders  is  such  that  the  force  of  friction,  as  we  have  seen  (p.  154,  Fig.  136), 
must  of  necessity  have  a  chipping  action.  Consequently,  whatever  be 
the  direction  of  the  furrows,  the  product  must  not  travel  under  the  im- 


168  FLOUR   MILLING  [CHAP,  iv 

pulse  of  the  forces  considered  above,  otherwise  the  stock  will  not  be  ground 
at  the  intersectional  points  of  these  furrows.  If,  on  the  other  hand,  the 
stock  is  so  fine  that  the  furrows,  being  rude  chisels,  are  unable  to  triturate 
it,  it  will  travel  in  the  furrow  because  of  the  effect  of  the  draught  of  air. 

In  this  way,  the  furrows  perform  the  duty  of  ventilating  canals  on 
the  one  hand,  and  serve  as  spouts  for  the  delivery  of  the  grist  out  of  the 
working  space,  on  the  other.  The  furrows  in  the  fixed  bed-stone  act  the 
part  of  the  ventilating  canals  and  exit  passages  for  the  product.  The 
upper  stone  furrows  serve  only  as  ventilating  canals  for  the  reduced  stock, 
and  ventilate  the  under  working  surface  of  the  stone  in  its  whole  area. 
Naturally  the  large  stock  caught  in  between  the  edges  of  the  furrows  is 
crushed ;  that  is  the  second  purpose  of  the  furrows. 

From  the  point  of  view  of  ventilating  the  working  area  of  the  stones, 
the  furrows  ought  never  to  be  made  curved,  because  this  lengthens  the  path 
of  the  passage  of  air.  From  this  point  of  view  straight  radial  furrows 
would  be  most  desirable.  But  such  furrows  would  form  no  angle  of 
intersection,  and  the  coincidence  of  the  upper  and  lower  furrows  would 
generate  a  series  of  whirls  in  their  common  canal,  for  the  motion  of  the 
air  in  the  furrow  of  the  rotating  stone  is  the  more  rapid,  owing  to  the 
centrifugal  power. 

Yet  another  significance  is  attached  to  the  furrows.  It  is  supposed 
that  the  grinder  intersected  by  furrows  acts  as  a  fan.  However,  this 
opinion  we  also  consider  to  be  erroneous,  for  the  chamber  out  of  which 
the  air  passes  into  the  working  space  through  the  eye  of  the  grinder  and 
the  space  into  which  the  air  passes  out  of  the  furrows,  are  one.  It  is  the 
chamber  of  the  casing.  And  if  the  set  is  aspirated  by  an  exhaust  and 
the  eye  is  isolated  from  the  chamber  of  the  casing  (Fig.  139),  the 
motion  in  the  air  is  brought  about  by  the  action  of  the  fan ;  the 
ventilating  effect  of  the  stone  is  almost  equal  to  zero  in  comparison 
to  the  airing  performed  by  the  fan. 

We  shall  direct  our  attention  to  rectilinear  furrows  as  being  the  most 
efficient,  but  seeing  that  in  general  practice  curved  furrows  have  to  be 
dealt  with,  the  practical  means  of  drawing  them  must  be  explained. 

The  furrows  shaped  in  a  logarithmic  curve  are  made  in  a  simplified 
manner  as  follows  (Fig.  145,  /)  :  at  the  end  of  the  radius  is  built  an  angle 
|,  equal  to  one-half  the  angle  of  inclination  of  the  furrows,  the  quotient 
of  which  is  to  be  found.  From  0,  the  centre  of  the  grinding  stone,  a 
perpendicular  is  dropped  on  the  line  5V.  The  line  OF  is  divided  into  an 
equal  number  of  parts,  five  in  the  present  case,  and  through  points  /, 
//,  ///,  and  IV  lines  parallel  to  5F  are  drawn.  Then  from  the  centre  0 


CHAP,  iv j  FLOUR   MILLING  160 

circles  are  described  with  the  radius  01,  Oil,  &c.,  and  01,  02,  03,  &c. 
Through  point  a  a  tangent  is  drawn  to  the  circle  OV,  which  crosses  the 
intermediate  circle  at  the  point  b  ;  from  b  a  tangent  is  drawn  to  the 
circle  01 V,  which  gives  us  the  point  i.  The  points  c,  h,  d,  &c.,  are  found 
in  the  same  manner. 

Joining  those  points  by  an  even  curve,  we  obtain  an  approximate 
construction  of  the  logarithmic  curve  of  the  furrow. 

Evans'  furrows  are  built  in  this  way  (Fig.  145,  IV).  A  circle  1  is  drawn 
with  the  radius  of  one-third  R  (JK=radius  of  the  stone),  and  circle  4,  one- 
fourth  R  in  radius.  The  space  between  circles  1  and  4  is  divided  into  an 
equal  number  of  parts  (three  in  the  drawing)  ;  in  a  like  manner  the 
space  between  the  circle  of  the  eye  /  and  that  of  the  stone  V  is  divided, 
but  with  one  more  part  than  the  preceding.  A  tangent  is  then  drawn 
from  point  V  to  the  circle  4  and  the  point 
a  obtained  ;  from  a  a  tangent  drawn  to  3 
forms  point  ft,  &c.  The  points  thus 
obtained  are  joined  and  form  8  V,  the  curve 
of  Evans'  furrow. 

The  novel  circular  furrows,  the  most 
popular  kind,  have  the  simplest  outlines 
(Fig.  145,  V).  From  the  centre  of  the  FlG  146 

millstone  0  a  radius  equal  to  3  inches  is 

projected.  Then  a  radius  equal  to  2R  +  3  inches  is  taken,  and  the  circles 
described  by  it  are  the  lines  of  the  furrows. 

The  practical  way  in  furrowing  the  stone  is  to  do  it  by  means  of  a 
timber  or  iron-plate  template  (Fig.  146),  which  is  prepared  according  to 
the  chosen  type  of  furrows.  In  forging  on  the  furrows  intersections  in 
them  ought  to  be  avoided,  for  the  angles  of  intersection  may  stop  the 
delivery  of  the  product. 

Tools  for  Dressing  Millstones. — The  grinding  surface,  having  become 
polished  from  work,  ceases  to  give  satisfactory  results  and  requires  dress- 
ing, which  the  miller  himself  usually  performs  by  hand.  For  this  pur- 
pose the  furrow  hammer  and  hoes  or  picks  of  different  kinds  are  used. 

The  tools  employed  for  renovating  the  worn  furrows  are  the  furrow 
picks  with  a  broad  edge  of  the  best  hardened  steel.  In  Fig.  147  two 
kinds  of  these  picks  are  shown  :  with  eyes  for  wooden  handles,  and 
solid.  For  solid  picks  wooden  handles  a  or  handles  with  a  metal 
head  b  are  used.  There  are  many  various  patented  hammer  holders,  but 
these  handles  too,  work  quite  satisfactorily.  The  picks  are  made  in 
sizes  up  to  250  mm.  along  their  edges  and  50  mm.  in  breadth. 


170 


FLOUR   MILLING 


[CHAP,  iv 


A  pick  is  a  hammer  with  the  striking  part  grooved  to  a  series  of 
pyramids,  and  is  used  for  roughening  the  polished  surface  of  the  mill- 
stone. The  number  of  pyramids  to  a  square  centimetre  amounts  some- 
times to  fifteen.  The  area  of  the  striking  part  reaches  8x8  cm.,  the 
length  of  the  hammer  15  cm.  The  striking  part  of  the  flat  hammer, 
as  well  as  the  edges  of  the  furrow  hammers,  are  made  of  the  best  hardened 
steel. 

Millstones  without  Furrows. — The  defects  of  the  grooved  millstones  lie 
in  their  tearing  the  integuments  with  their  edges,  and  grinding  them 
too  finely.  The  sifting  away  of  the  bran  reduced  to  flour  becomes 


Picks 


FIG.  147. 

impossible,  owing  to  which  the  meal  acquires  a  dark  colouring.  A  pre- 
liminary crushing  of  the  grain  in  the  heart  has  the  same  effect.  Besides 
that,  the  grain  being  but  slowly  delivered  by  the  heart,  a  considerable 
part  of  the  working  surface  is  left  without  stock,  and  therefore  the 
capacity  of  the  millstones  in  spite  of  their  large  working  area  is  insigni- 
ficant in  comparison  with  roller-mills.  With  a  view  to  avoiding  these 
defects  an  engineer,  I.  Noll,1  proposes  to  abolish  the  furrows  and  the 
heart  and  diminish  the  working  area.  Instead  of  a  heart  (Fig.  148)  I. 
Noll  sets  on  the  spindle  a  disc  of  zinc  sheet-iron  a,  1040  mm.  in  diameter 
(the  diameter  of  the  millstones  is  1300  mm.).  This  disc  by  gyrating  and 
developing  a  centrifugal  force  in  the  grain  feeds  it  into  the  grinding 
circle,  the  breadth  of  which  is  70  to  100  mm.  I.  Noll  maintains  that 

1  Die  Muhle,  1911,  No.  40. 


.  IV] 


JFLOtJR   MILLING 


171 


the  capacity  of  such  a  stone  is  considerably  higher  than  that  of  a  common 
grinder. 

The  disc  a  is  set  on  a  cast-iron  washer  b.  The  part  e  of  the  millstone 
is  of  concrete,  and  /  of  plaster-stone.  Such  a  construction  diminishes 
the  weight  of  the  stone  and  simplifies  its  a\  ^  $  >f 

dressing. 

The  idea  of  such  grinders  deserves  careful  atten- 
tion. Too  small  a  number  of  experiments,  how- 
ever, has  been  performed,  to  allow  us  sufficient 
grounds  completely  to  reject  the  old  construction 
of  millstones. 

The  Erection  of  Millstones. — A  correct  fitting 
up  of  the  millstones  and  the  balancing  of  their 
motion  is  of  great  importance. 

The  fixing  up  and  balancing  of  the  stationary 
stone  is  very  easy.  Only  a  spirit-level  is  required 
here  for  establishing  the  working  surf  ace  in  a  hori- 
zontal plane  and  a  plumb-bob  for  centring  it.  The 
setting  of  the  rotating  stone  is  much  more  difficult. 

If  we  set  the  lower  working  surface  of  the  runner  in  a  horizontal 
plane  while  at  rest,  this  surface  may  assume  a  slanting  position  when 
rotating,  should  the  structure  of  the  stone  not  be  uniform,  as  frequently 
happens.  This  phenomenon  is  easily  explained.  Supposing  we  have 
(Fig.  149)  a  wire  cylinder  k  k1  Tc2  ks  set  on  a  spindle  A  with  the  aid  of  a 
movable  connection  c.  At  points  k±  k2  there  are  equal  weights  attached 


FIG.  148. 


A 
FIG.  149. 


In  a  state  of  repose  the  cylinder  will  be  balanced,  i.e.  its  axis  will  coincide 
with  the  axis  of  the  spindle.  But  as  soon  as  we  commence  revolving  it, 
the  cylinder  will  slant  (Fig.  150),  because  the  centrifugal  forces  T  at 
points  &!  and  &3  form  a  couple  of  forces  the  shoulder  of  which  is  equal  in 
size  to  k±  kz. 

The  axis  of  rotation  of  the  couple  T  kl  k2  will  be  in  the  fulcrum  point 


FLOUR   MILLING  [CHAP,  iv 

of  support  c  of  the  spindle.     To  obviate  slanting  similar  weight  must  be 
attached  at  the  points  k  and  k2. 

It  is  necessary  to  find  a  general  solution  of  the  problem,  which  would 
show  how  the  supplementary  weights  are  to  be  disposed  in  the  grinder, 
so  as  to  attain  an  equiponderate  motion.  Let  us  suppose  we  have  an 
immobile  axis  00  x  (Fig.  151),  and  a  stone  A  of  irregular  shape  rotating  on 
it.  The  centrifugal  power  developed  exercises  a  pressure  upon  the  axis. 
If  we  mark  the  reaction  of  the  axis  by  forces  P1  and  P2,  applied  in  the 

fulcrum  of  the  axis  0  and  015 
then,  including  those  forces 
in  the  number  of  active 
forces,  we  may  regard  the 
whole  system  as  free,  and 
apply  to  it  D'Alambert's 
principle.  The  motion  of  the 
stone  being  a  steady  rotation, 

l  the  sum  total  of  projections 

and  the  sum  total  of  moments 

in  respect  to  the  three  reciprocally  perpendicular  axes  OZ,  OX,  0  Y  must 
be  equal  to  zero.  By  denoting  the  angular  velocity  of  rotation  through 
co,  through  m  the  mass  of  any  particular  part  of  the  stone,  x,  y,  z  its 
co-ordinates  in  respect  to  the  corresponding  axes,  P  the  weight  of  the 
whole  stone,  a  and  b  the  distance  of  the  centre  of  gravity  of  the  stone 
from  the  planes  yoz  and  xoz,  M  its  mass,  and  h  the  quality  00  lt  we  obtain 
the  following  equations  : 

The  sum  total  of  projections  : 


0    ......  (1) 

O    .         .         .         .         .         .  (2) 

P-Z=0  .....          .          .          .  (3) 

The  sum  total  of  moments  : 


0          .....     (4) 
0          .....     (5) 

The  moments  of  each  acting  force  in  respect  to  the  axis  OZ  are  equal 
to  zero,  for  the  direction  of  those  forces  intersects  the  axis  OZ. 

If  the  axis  of  rotation  passes  through  the  centre  of  gravity,  a  and  b 
are  equal  to  zero  ;  the  forces  X19  X2,  Y1  and  Y2  then  are  equal  to  zero. 
If,  at  the  same  time,  OZ  is  the  main  axis  of  inertia,  then  2myz=§  and 
Zmxz  =  Q.  Under  such  conditions  the  axis  of  rotation  of  the  stone  will 
be  exposed  to  no  side  pressures,  i.e.  we  obtain  a  free  axis. 


CHAP.    IV] 


FLOUR    MILLING 


173 


As  regards  the  millstone  the  first  condition  is  fulfilled  when  the  axis 
of  the  spindle  coincides  with  the  axis  of  the  stone,  i.e.  passes  through  its 
centre  of  gravity.  Should  the  grinder,  however,  be  of  different  density 
Smyz  and  Zmxz  will  differ  from  zero.  The  millstone  will  then  slant  like 
the  wire  cylinder.  In  that  case  supplementary  weights  must  be  added. 

If  a  and  b  are  equal  to  zero,  we  shall  obtain  from  equations  (1)  and  (2)  : 

X1  =  — X2,  and  YI  =  —  Y2. 

The  resultants  of  X1  and  Ylt  X2  and  72  will  be  Px  and  P2.  A  couple 
of  forces  are  thus  obtained,  which  tend  to  overthrow  the  axis  of  the  stone. 
For  counteracting  this  couple  of  forces  (Fig.  151)  there  might  be  applied 
weights  Ml  and  M  2  of  a  size  which  would  produce  centrifugal  forces 
oPM-iT,  equal  to  Px  and  P2. 

In  general  practice  the  supplementary  weights  are  applied  by  means 
of  a  special  adjustment  in  the  revolving  grinder. 

Three  or  four  cavities  are  made  in  the  stone,  in  which  cast-iron  boxes 


FIG.  152. 


FIG.  153. 


(Fig.  152)  A  covered  with  a  lid  B  are  deposited.  In  such  a  box  there  is  a 
cast-iron  weight  p,  which  is  adjustable  along  the  rod  a  to  the  right  or 
left  and  up  or  down  with  the  aid  of  screws  b  and  nuts  c.  By  moving  the 
weight  p  to  the  periphery  of  the  millstone  we  augment  its  centrifugal 
force,  while  by  moving  one  weight  up,  and  the  other,  on  the  opposite  side 
of  the  stone,  down,  we  lengthen  the  shoulder  of  the  counterbalancing 
couple. 

Another  appliance  is  shown  in  Fig.  153.  The  weight  H  here  slides 
along  the  rod  F  with  a  collar  t,  which  rests  on  a  spring  E  and  is  fixed  to 
the  rod  by  a  bolt.  The  rod  passes  through  a  cast-iron  ball  which  is  held 
by  a  bearing  D.  In  the  opposite  side  of  the  box  there  are  openings  J. 
By  placing  the  end  of  the  rod  in  different  sockets,  the  height  of  the  weight 
may  be  altered. 

Simpler  appliances  consist  of  boxes  with  lead  in  them,  the  quantity 
of  which  may  be  either  increased  or  diminished.  Sometimes  there 
simply  are  cavities  made  in  the  stone  and  filled  with  melted  lead.  If  too 


174 


FLOUR   MILLING 


[CHAP,  iv 


much  lead  is  poured  in,  part  of  it  is  cut  but;    if  too  little,  more  is 
added. 

On  Fig.  154,  showing  the  building  of  a  millstone  of  pieces  of  French 
stone,  we  see  the  cast-iron  boxes  E  for  lead,  which  are  hermetically  set 

in   when  the   top   part   of   the   stone  is 
covered  with  concrete. 

When  the  stone  (runner)  is  ready,  it 
is  balanced  in  the  following  way  (Fig.  155). 
An  apparatus  consisting  of  three  plates 
ef,  cd}  and  ab,  and  two  bolts,  g  and  h,  is 
set  in  the  eye  of  the  stone.  The  plate  cd 
slides  freely  on  the  bolts  and  is  kept  back 
by  nuts  k.  By  the  upper  nuts,  the  appar- 
atus is  screwed  up  in  the  eye.  Then  the 
stone  is  placed  on  a  bursting,  in  which  an 
iron  rod  m  is  set  upright,  tapering  to  its 
point  n.  The  rod  passes  through  the 
opening  0  in  the  plate  ab  and  rests  with 
its  point  n  in  the  small  cavity  made 
with  a  centre-mark  in  the  plate  cd.  This 
plate  must  be  set  so  that  its  centre  (the  cavity  for  n)  would  correspond 
to  the  fulcrum  of  the  driving  iron.  The  rod  mn  rests  with  its  lower  end 
on  a  lever  which  lifts  it  together  with  the  stone.  The  stone  raised  by 


FIG.  154. 


llr 


FIG.  155. 


the  rod  is  carefully  revolved  and  watched,  to  see  if  it  slants.  In  case 
of  a  slant,  the  position  of  the  apparatus  is  altered  in  the  direction 
required  and  the  weights  in  the  boxes  are  transposed,  the  stone  having 
been  previously  lowered  on  to  the  bursting,  and  the  upper  screws 
loosened. 

These  manipulations  are  repeated  until  the  stone  rotates  without  a 


CHAP.    IV] 


FLOUR   MILLING 


175 


slant.     Once  the  right  centre  of  the  driving  iron  is  found,  the  stone  is 

lifted  oft  the  rod  mn,  placed  on  its  side,  and  a  circle  is  drawn  with  a  pair 

of  compasses  from  the  centre  n  of  the  plate  cd  on  the  grinding  surface  of 

the  stone.     On  this  circle  in  two   or  three  places   holes   are    drilled, 

3  to  4  mm.  in  diameter  and 

7  to  8  mm.  deep,  filled  with 

melted      lead,      which       is 

smoothed  to  the  face  of  the 

stone  and  then  the  circle  on 

them    is    redrawn.       These 

lead  dots  serve   for  proving 

the  centre  of  the  cross-head 

in  marking  the  spot  for  it. 
Fixing    the   bed -stone. — 

In   fixing    up   a    stone   mill 

either  on   the   floor   of    the 

mill  or   on  a   hursting   pre- 
pared for  it,  a  circular  hole 

is    made    in   the    boards    d 

(Fig.    156),   and  a   cast-iron 

ring  c  is  placed  in  it  with  a 

flange  in  which  holes  r  are 

drilled    for    the    bolts,    by 

means  of  which  the  circle  is 

fixed  to  the  hursting.  Besides  FlG<  156< 

those  small  holes  there  are 

three  larger  ones  for  bolts  e,  which  support  the  cast-iron  frame  /with  ribs  g 

on  its  lugs  t.     By  tightening  the  bolts  e  the  working  surface  of  the  stone 

may  be  brought  to  a  horizontal  position.     For  adjusting  the  axis  of 

the  stone,  there  are  wedges  i  (six 
in  number)  placed  in  between  the 
grinder  and  the  ring  c.  If  the 
stone  is  to  be  moved  to  the 
left,  for  instance,  the  two  wedges 


FIG,  157. 


on  the  left  side  are  loosened,  while  the  other  four  are  driven  in  deeper 
with  lead  hammers. 

A  better  frame  is  shown  in  Fig.  157.  It  is  a  cast-iron  cylinder  with 
a  perforation  in  the  bottom  for  the  spindle.  The  frame  is  fixed  to  the 
floor  with  bolts,  which  are  screwed  into  the  lugs  c.  At  three  points  of 
the  bottom  there  are  ribs  a  with  holes  for  the  bolts,  by  means  of  which 


176 


FLOUR   MILLING 


[CHAP,  iv 


the  working  surface  of  the  stone  is  set  in  a  horizontal  plane.  In  the 
sides  of  the  cylinder  are  three  holes  for  bolts,  which  help  to 
centre  the  stone.  To  make  the  construction  lighter,  the  solid 
bottom  of  the  cylinder  may  be  substituted  by  three  lugs.  A 
still  lighter  design  is  represented  on  Fig.  156.  There  are 
simply  three  castings  A  made  with  regulating  bolts.  These 
lugs  are  set  independently  on  the  floor  in  a  circle  at  an 
angle  of  180°. 

For  the  plainest  kinds  of  machinery  in  peasant  mills,  a 
simple  planting  on  beams  may  be  recommended.  The  ad- 
justing borts  may  be  let  through  the  beams  into  which 
threaded  nuts  are  set. 

The  dimensions  in  all  the  figures  are  given  in  mm. 
The  spindle  supporting  the  runner  is  an  iron  or  steel  shaft  A 
(Fig.  158)  with  a  vertical  journal  a  set  in  its  base.  The  top 
part  of  the  shaft  B  is  turned  to  a  cone  or  planed  smooth  to 
a  truncated  pyramid.  In  the  first  case  it  is  coupled  with 
the  cross-head  of  the  driving  iron  by  means  either  of  a  wedge 
or  a  key. 

The  mill-bush  (Figs.  159  and  160),  stationed  in  the  eye  of 
FIG.  158.  fae  bed-stone,  and  arresting  the  side-movement  of  the  shaft, 
has  timber  (oaken,  beech-tree,  or  pock-wood)  or  bronze  wedge-shaped 


FIG.  159. 


FIG.  160. 


bushes  a.      In  it  the  centring  of  the  shaft  is  done  with  the  aid  of  bolts 
0  and  nuts  6.     This  mill-bush  is  attached  to  the  stone  by  means  of  lugs  d, 


CHAP.    IV] 


FLOUR   MILLING 


177 


which  are  covered  with  a  cementing  composition  in  their  respective  seats 
in  the  stone.     The  lubricant  is  poured  into  the  cup  e. 

There  are  mill-bushes  of  various  design  but  always  with  bushes. 
Sometimes   those   mill-bushes  are   set   on  the  frame. 

A  step-bearing  of  the  ordinary  kind  is  shown  in 
Fig.  161.  A  is  the  lower  end  of  the  shaft,  into  which 
is  set  a  journal  B,  resting  on  a  steel  bush  c.  The 
side-bush  d  is  of  bronze.  The  oil  is  poured  into  s, 
and  after  passing  through  the  bearing  is  drained 
through  drilled  canals  /.  The  hole  g  in  the  end  of  the 
shaft  is  to  afford  access  to  the  journal  B,  which  is 
knocked  out  with  a  wedge-shaped  plug  in  case  a 
breaking  off  must  be  made.  The  liner  E  of  the  step- 
bearing,  cylindric  in  shape,  is  generally  of  cast  iron. 
The  frame  of  the  step-bearing  is  shown  in  Fig.  162. 
The  spindle  is  lifted  by  a  lever  D.  The  bearing  F 
supports  the  shaft  of  the  toothed  gearing  to  the  spindle. 

The  design  of  the  step-bearings  varies  very  much, 
but  the  ball  collar  thrust-bearings  are  to  be  preferred 
most. 

The  driving  iron. — By  means  of  the  driving  iron 
the  spindle  is  connected  with  the  rotating  stone.  The  plainest  style 
of  a  driving  iron  (Fig.  163)  is  an  iron  cross-head  which  is  hermeti- 
cally set  in  the  grinder,  or  a  tripod  driving  iron  (Fig.  164),  also 
tightly  fitted  in  the  stone.  But  these  designs  should  be  avoided, 
for  the  proper  balancing  of  a  fast  coupled  runner  in  m.otion  is '[an 


FIG.  161. 


-     FIG.  162. 

impossibility.  A  type  of  driving  iron  in  vogue  is  shown  in 
Figs.  165  and  166.  In  the  stone  there  are  set  two  cast-iron  cups  N, 
on  which  the  journals  e  of  the  cross-head  b  rest.  This  cross-head 
likewise  has  sockets  for  journals  e  of  a  second  cross-head  c.  The 
spindle  is  set  with  its  conic  end  in  the  cross-head  c,  and  fastened  to  it 

M 


178 


FLOUR   MILLING  [CHAP,  iv 

This  forms  a  flexible  fastening  on  the  principle 


with  one  or  two  keys, 
of  Hooke's  joint. 

Instead  of  cups  a  it  is  better  to  set  (Fig.  167)  a  cylindric  cast-iron 
ring  B  with  ribs  P  for  the  journals  of  the  cross-head.  In  that  case  the 
load  chipping  the  stone  is  distributed  over  a  larger  area.  The  second 


FIG.  163. 


FIG.  164. 


FIG.  165. 


cross-head  D  here,  is  coupled  to  the  spindle  by  wedges  i,  though  keys  t 
may  also  be  employed. 

To  prevent  any  curling  up  of  the  ring,  it  is  provided  with  protruding 
ribs  which  are  sunk  into  sockets  hollowed  out  in  the  stone  for  that 
purpose,  and  fixed  there  with  cement  when  the  ring  is  laid  on. 

In  the  upper  cross-head  of  the  driving  iron  there  is  usually  made  a 


FIG.  166. 


FIG.  167. 


hole  K  for  setting  the  plate  e  (Fig.  167)  which  receives  and  flings  the 
grain  by  centrifugal  force  into  the  eye  of  the  millstone.  Sometimes  a 
cup  (Fig.  168)  is  set  in  the  place  of  a  flat  plate.  The  advantages  sup- 
posed to  be  afforded  by  this  cup  are  that  the  heavy  extraneous  matter 
(stones,  small  pieces  of  iron,  &c.)  drop  to  its  bottom  and  do  not  reach 
the  milling  area.  This  is,  however,  an  unnecessary  complication  of 
the  design,  because  previous  to  being  milled,  the  grain  has  to  be  freed 
of  all  impurities.  And  if  unclean  grain  is  milled  (as  in  primitive 


CHAP.    IV] 


FLOUR   MILLING 


179 


peasant   mills),  this   cup   is   too   small  to  serve  as  a  heavy  impurities 
collector. 

The  feeding  of  the  millstones  is  done  through  feeding  tubes  or  other 
more  complicated  mechanisms.  Fig.  169  represents  an  iron  feeding 
tube  B  with  a  hopper  B±.  With  a  view  to  regulating  the  feed,  the 


FIG.  168. 


FIG.  169. 


distance  between  the  end  of  the  tube  and  the  plate  is  measured  by 
means  of  a  cast-iron  sleeve  b  having  a  square  thread,  firmly  joined  to 
the  tube,  and  a  hand-wheel  T,  with  an  inversely  threaded  hub,  which 
is  held  by  the  collars  of  the  cast-iron  cross-head  M .  By  rotating 
the  hand-wheel,  the  tube  may  be  raised  or  lowered,  thus  regulating 
the  diameter  of  the  stream  of  product  between  the  tube  and  the  plate. 


^W^VtU          *2 

3 


FIG.  170. 


The  ordinary  feeding  device  employing  a  rocking  shoe  is  shown  in 
Fig.  170.  The  hopper  A  is  set  on  a  small  timber  frame  which  stands  on 
the  cover  of  the  casting.  Under  the  hopper,  on  three  or  four  rods 
(bolts  i  and  two  rods  k)  the  shoe  B  is  suspended  aslant.  To  the  pro- 
truding plank  of  the  shoe  g  is  attached  a  square  block  d,  which  receives 
the  blows  from  a  cross-head  set  on  an  axle,  which  in  its  turn  is  set  in  a 
plate.  In  the  cross  bar  of  the  frame,  h  serves  as  an  upper  bearing  to  the 


180' 


FLOUR    MILLING 


[CHAP,  iv 

axle.  A  slide  a,  lowered  or  lifted  with  the  aid  of  a  hand- wheel  b,  regulates 
the  flow  of  product.  The  inclination  of  the  shoe  is  adjustable  by  means 
of  belts  /,  which  may  be  wound  on  and  off  the  axle  c  by  turning  it  with 
the  hand- wheel  e  and  keying  on  with  wedges  I. 

Another  feeding  appliance  we  see  in  Fig.  171.  Here  we  have  a  cast- 
iron  trunk  A  mounted  on  the  cover  of  the  casing  by  its  wall-brackets. 
The  spout  T  is  cast  jointly  with  the  trunk.  Through  the  bottom  of  the 
trunk  is  let  an  axle  v  connected  by  sleeve  m  with  an  axle  v^  running 
from  the  driving  iron.  The  sprocket  b  feeding  the  grain  into  the  spout  T, 


FIG.  171. 

and  the  cross-head  a  which  loosens  the  grain  fed  into  the  trunk,  are 
both  set  on  the  axle  v.  By  raising  and  lowering  axle  v  with  lever  d, 
attached  with  its  fork  to  the  spout,  the  flow  of  product  is  regulated. 

The  gate  valve  e  held  by  a  screw  n  regulates  the  delivery  of  the  grain 
into  the  spout ;  the  lid  g  is  an  inspecting  door,  r  the  lubricator  oiling 
the  axle  v. 

3.  Under-Runner  Millstones 

In  studying  designs  of  stone  mills  we  saw  that  the  product  treated 
travels  to  the  outlet  from  the  working  space  under  the  action  of  the 
force  of  friction,  if  large  enough  and  subjected  to  pressure  between  the 
stones,  or  travels  down  the  furrowrs  of  the  stone  and  the  working  surface 
of  the  bed-stone,  driven  by  an  air-current  if  it  is  so  finely  broken  that 
the  top  runner  cannot  act  upon  it. 

In  the  stone  mills  with  an  under  runner,  the  delivery  of  the  milled 
product  takes  place  under  much  more  favourable  conditions,  since  its 
particles  acquire  a  centrifugal  force.  As  to  the  large  stock  to  be  milled, 


.  iv] 


FLOUR    MILLING 


181 


its  treatment  also  obtains  under  better  conditions,  for,  owing  to  the 
centrifugal  force,  the  pressure  being  equal  to  that  of  the  upper- 
runner  mills,  it  is  treated  more  vigorously,  and  the  actual  grinding 
takes  less  time. 

In  respect  of  under  runners,  the  important  question  as  to  the  outline 
of  the  furrows,  and  even  their  indispensability,  arises.  If  in  a  mill  with 
a  fixed  bed-stone  the  ventilating  air  carries  the  fine  ground  product 
out,  in  the  case  of  a  rotating  under  stone  the  unground  particles  of 
grain  will  be  ejected  by  centrifugal  force  if  the  line  of  the  furrows 
coincides  with  the  direction  of  the  product  which  is  propelled  by  centri- 
fugal force,  and  by  the  pressure  of  air.  Owing  to  this,  if  the  line  of 
the  furrow  is  badly  chosen,  the  finished  product  will  be  unsatisfactory, 
i.e.  it  will  be  intermixed  with  unground  particles  of  grain. 

To  solve  the  question  of  the  pattern  of  the  furrows  we  must 
know  the  direction  in  which  the 
product  travels,  and  then  a  design 
of  furrows  can  be  selected  which 
will  result  in  the  crossing  between 
the  route  of  the  grain  and  the  direc- 
tion of  these  furrows.  Only  in  this 
way  will  the  unground  product  be 
ejected  from  the  furrows  to  be  re- 
duced  to  flour  in  the  grinding  area. 

Professor  Kick  gives  the  following  solution  of  the  problem  concern- 
ing the  route  of  the  stock. 

o 

Let  us  suppose  that  the  under  stone  rotates  with  an  angular  velocity. 
If  a  particle  of  product  at  a  distance  r  from  the  axis  of  rotation  acquires 
a  centrifugal  force  ma)2r,  equal  to  the-  friction  force  fmg,  it  is  bound  to 
slip  off  the  stone  at  that  moment,  and  move  uniformly,  i.e.  as  a  free 
body,  with  a  speed  ro>,  so  that  its  motion  will  be  directed  at  a  tangent 
to  the  circumference  of  the  radius  r.  The  denotations  employed  here 
are  :  m,  the  mass  of  particles  ;  g,  the  acceleration  of  gravity  ;  and  /,  the 
coefficient  of  friction  between  the  product  and  the  stone. 

The  free  motion  of  the  particle  in  respect  to  the  uniformly  rotating 
stone  is  an  involute  of  circle,  a  fact  easily  grasped  (Fig.  172). 

The  stone  revolves  as  pointed  by  arrow  8.  The  particle  m  having 
slipped  off  at  point  a1}  at  a  distance  r  from  the  axis  of  rotation,  flies 
at  a  tangent  a3  in  the  direction  the  stone  moves,  with  the  speed  rco. 
The  motion  of  a3  is  absolute.  To  find  the  trajectory  of  motion  in 
respect  to  the  rotating  runner,  let  us  suppose  that  in  a  unit  of  time  the 


FlG  172> 


182  FLOUR    MILLING  [CHAP,  iv 

runner  has  turned  at  an  angle  a,  and  the  particle  m  has  travelled  the 
distance  alf  Then  the  resulting  position  mx  of  the  particle  will  be  at 
the  intersecting  point  of  the  circle  described  with  radius  ol  and  the 
circle  drawn  from  centre  b  of  the  radius  of  the  straightened  arc  6a1? 
corresponding  to  the  angle  a.  A  series  of  points  al9  a2,  «3,  &c.  obtained  in 
this  manner,  forms  an  involution  of  circle. 

This  opinion  of  Professor  Kick's  cannot  be  agreed  with,  for  he  has 
not  taken  into  consideration  the  power  of  wind  which  will  impart  a 
uniformly  accelerated  motion  to  the  particle  m. 

Besides  that,  taking  for  granted  that  the  particle  will  slip  off  the 
surface  of  the  stone  (which  is  impossible,  the  gravity  playing  a  part 
here),  it  will  move  in  a  parabola  under  the  effect  of  the  power  of  gravity 
and  of  wind  and  will  certainly  fall  upon  the  stone. 

Consequently  we  see  that  the  trajectory  of  motion  of  the  particle, 
influenced  by  its  gravity,  centrifugal  force,  and  the  power  of  wind,  pre- 
sents a  .very  complicated  curve,  and  in  no  case  an  involute  of  circle,  as 
Professor  Kick  supposes.  It  is  possible  to  construct  this  curve  in  theory 
for  one  particle.  But  if  we  consider  that  in  the  working  area  of  the 
stones  there  is  a  large  quantity  of  product  undergoing  friction  in  its 
mass,  and  that  the  rough  surface  of  the  millstone  excludes  the  very 
idea  of  friction  in  the  fine  particles,  for  the  cutting  crystals  of  the  stone 
impede  the  motion  of  the  reduced  particles,  and,  consequently,  exclude 
the  possibility  of  friction  in  the  sliding  motion  over  the  surface  of  the 
stone  (the  motion  must  be  performed  in  a  zigzag  line  between  the 
crystals),  these  circumstances  make  the  problem  insoluble. 

As  to  general  practice,  it  would  have  been  possible  to  answer  the 
question  respecting  the  most  advantageous  tracing  of  furrows,  had  strictly 
scientific  experiments  been  performed  to  that  end.  However,  in  our 
opinion,  the  furrows  ought  to  be  completely  discarded  on  the  lower 
runner,  and  retained  only  on  the  upper  fixed  stone  for  ventilating  the 
working  area :  the  shape  of  the  furrows  in  the  fixed  upper  stone,  at  the 
same  time,  being  of  no  great  importance,  they  may  therefore  be  of  the 
simplest  kind,  i.e.  rectilinear. 

Before  proceeding  to  describe  the  designs  of  under-runner  mills,  we 
must  mention  the  experiments  performed  by  Buisson  in  connection 
with  his  observations  concerning  the  influence  of  exhausting  mill- 
stones. 

All  the  three  types  of  stone  mills  were  driven  by  6  h.p.  each.  The 
experiments  were  made  on  wheat  grinding,  and  the  stones  employed 
were  French,  of  equal  diameter,  and  with  similar  furrows. 


CHAP,  iv]  FLOUR    MILLING 

The  results  of  an  hour's  grinding  were  as  follows  : 

(1)  An  upper-runner  mill  without  exhaust  yielded  182  Ib. 

(2)  An  upper-runner  mill  with  exhaust  yielded  279  Ib. 

(3)  An  under-runner  exhausted  mill  yielded  373  Ib. 

(4)  The  last  mill,  with  both  the  upper  and  lower  stones  revolving 
in  opposite  directions,  with  ventilation,  yielded  468  Ib.  per  hour. 

As  regards  the  fourth  case,  the  flour  produced  was  of  a  worse  quality 
than  in  the  first  three  cases. 

These  experiments  prove  that  stone  mills  with  revolving  upper  and 
lower  grinders  ought  not  to  be  employed,  because  of  the  low  quality 
of  the  grist.  Besides,  these  mills  are  so  complicated  in  design  that  in 
this  respect,  likewise,  they  may  be  regarded  as  unsatisfactory.  At  any 
rate  they  were  rejected  long  since  in  general  practice,  and  we  shall  pass 
them  by. 

In  comparing  the  capacity  of  upper-runner  and  under-runner  mills, 
we  notice  that  the  capacity  of  the  latter  exceeds  the  former  by  33*5  per 
cent.  Buisson's  experiments  are  naturally  insufficiently  exact,  for  he 
used  stones  with  uniform  furrows,  but  undoubtedly  under-runner  mills 
grooved  in  the  most  advantageous  manner  would  yield  a  larger  quantity 
of  product  of  a  higher  quality.  But  the  comparatively  great  pressure  of 
the  spindle  upon  the  vertical  journal  is  a  defect  in  the  design  of  under- 
runner  mills. 

Indeed,  if  to  a  unit  of  working  surface,  the  pressure  of  the  upper 
runner  necessary  for  grinding  the  product  is  p  and  the  weight  of 
the  stone  to  the  same  surface  P,  then  the  pressure  of  the  spindle  upon 
the  vertical  journal,  the  common  working  area  being  w,  will  be  (P-p)w, 
because  p  is  the  reaction  of  crushing  of  the  bed-stone.  If,  on  the  other 
hand,  we  have  an  under  runner,  then  the  pressure  upon  the  vertical 
journal  may  be  expressed,  employing  the  same  denominations,  by  the 
formula  (P+p)w,  for  the  weight  of  the  stone  and  the  reaction  of  its 
pressure  upon  the  grain  both  act  in  the  same  direction.  Owing  to  this, 
the  vertical  journal  becomes  worn  much  faster  in  under-runner  mills 
than  in  those  with  upper  runners.  However,  this  defect  is  reparable,  as 
will  be  seen  in  the  constructive  description  of  stone  mills. 

An  ordinary  type  of  an  under-runner  mill  is  shown  in  Fig.  173.  The 
stationary  top  stone  B  is  encircled  with  an  iron  ring  a  (set  on  the  stone 
hot)  with  three  clutches  q.  The  cast-iron  casing  c  serves  as  frame  to  the 
upper  stone  ;  the  stone  rests  on  the  casing  on  bolts  b,  by  means  of  which 
the  working  surface  of  the  stone  may  be  set  horizontally.  The  chamber 
of  the  casing  is  closed  by  a  timber  ring  d.  The  runner  C  is  supported  on 


184 


FLOUR   MILLING 


[CHAP,  iv 


an  ordinary  balancing  driving  iron  e,  the  first  cross-head  of  which  rests 
on  a  disc  i,  furnished  with  a  lid  which  serves  at  the  same  time  as  a  plate 
supplying  the  grinding  area.  In  its  bottom  surface  the  runner  has  boxes 
with  weights  for  counterbalancing  it.  In  the  sides  of  the  stones  there 
are  iron  sockets  n  for  lifting  it.  Every  stone  ought  to  be  provided  with 
such  sockets,  because  in  mounting  or  dismantling  of  the  mills  the  stones 
must  necessarily  be  lifted. 

The  feeding  is  performed  by  the  tube  A  described  earlier  (Fig.  169). 
The  side -travellings  of  the  spindle  D  are  arrested  by  an  ordinary  vertical 
bearing  k.  On  the  spindle  is  set  a  washer  I,  its  turned  down  ends  entering 
the  ring  reservoir  m,  which  is  filled  with  water  (or  empty)  to  prevent  the 
meal -dust  from  penetrating  into  the  bearing.  As  to  the  remaining 

details,  the  shafting  of  the  rotation 
of  the  spindle,  the  step-bearing 
and  the  tram  pot  not  given  in  the 
drawing,  they  are  similar  to  those 
of  the  above  examined  upper- 
runner  mills. 

The  constructive  advantages 
of  under-runner  mills  are  the 
following  : 

(1)  Simplicity  of   the   bearing 
substituting  the  complicated  mill- 
bush  here,  and  its  accessibility  for 
inspection  and  lubrication. 
(2)  The  driving  iron  does  not  impede  the  free  passage  of  the  product 
through  the  eye,  and  consequently  the  grinding  surfaces  are  more  evenly 
supplied  with  grain. 

The  heavy  loading  of  the  step-bearing  is,  as  we  have  seen,  an  important 
defect  more  or  less  successfully  combated  almost  exclusively  by  Russian 
engineers.  To  counteract  the  rapid  wearing  of  the  vertical  journal  and 
the  step-bearing  resulting  from  the  heavy  load,  they  replaced  the  sliding 
friction  by  a  rolling  friction,  employing  ball  collar  thrust-bearings  of  a 
corresponding  design. 

Fig.  174  represents  an  under-runner  mill  designed  by  Mr.  Panshin. 
The  revolving  under  stone  A  is  fixed  on  a  cast-iron  frame  B  forming  one 
block  with  the  pulley  D,  which  is  set  into  motion  from  a  belt  drive.  The 
whole  system  is  mounted  on  a  cast-iron  frame  E  bolted  to  the  foundation. 
The  frame  supporting  the  runner  A  rests  on  two  ball  collar  thrust-bearings, 
the  first  one,  /,  being  set  below  on  the  main  frame,  the  second,  77,  on  the 


FLOUR   MILLING 


185 


CHAP.    IV] 

vertical  stationary  cylindric  steel  column  with  a  collar.  The  hardened 
steel  balls  receiving  the  pressure  of  the  under  runner,  roll  between  the 
steel  rings,  likewise  hardened.  In  this  wise  the  pressure  of  the  under 
runner  is  supported  by  two  horizontal  planes,  which  reduces  the  wear 
of  the  steel  balls  and  rings.  The  third,  upper,  row  of  balls  ///,  also 
rolling  in  steel  washers,  does  duty  for  the  mill-bush.  The  distance  be- 
tween the  grinding  surfaces  is  adjusted  with  the  aid  of  a  cogged  hand- 
wheel  0,  having  a  long  square-threaded  hub.  The  hand-wheel  is  turned 


FIG.  174 

by  a  lever  H.  The  lifting  is  done  as  follows  :  the  tripod  drop-hanger 
frame  K  supporting  the  fixed  upper  stone  is  screwed  with  its  hub  on  the 
hub  of  the  hand- wheel  0  and  lifts  the  stone  ;  with  the  retrograde  motion 
of  the  hand-wheel,  the  drop-hanger  frame  is  screwed  off  and  the  upper 
stone  is  lowered.  The  regulation  of  the  flow  of  grain  is  performed  by 
lowering  or  raising  the  feed-tube  L  with  a  hopper,  which  is  done  with  a 
hand- wheel  having  a  screw  thread  on  the  inside  of  its  hub. 

The  lubrication  of  the  mill-bush  and  step-bearings  is  sufficiently 
clearly  depicted  in  the  drawing.  To  the  bottom  of  the  frame  on  which 
the  runner  is  mounted  are  riveted  iron  scrapers  M,  which  convey  the 
flour  to  the  discharge  spout  T. 


186  FLOUR    MILLING  [CHAP.  iV 

W.  Joukovsky's  stone  mill  (engineer  Fuhrman's  patent)  has  a  fixed 
frame  T  carrying  (Fig.  175)  a  step-bearing  R  with  three  rows  of  balls. 
The  frame  P  is  cast  in  a  single  block  with  the  pulley  8  of  pig  iron  ;  the 
cylindric  rib  U  of  the  frame  constitutes  the  mill-bush  K.  The  steel 
shaft  V,  connected  with  the  frame  T  by  means  of  keys,  is  stationary,  and 
has  an  axle  V1  inside,  which,  with  the  aid  of  a  ratchet  wheel  gearing  a  and 
lever  h,  may  rise  and  fall  by  being  screwed  into  the  screw  hub  b  of  the 
shaft  V. 

The  shaft  Vt  supports  the  fixed  upper  stone  on  a  tripod  drop-hanger 
frame,  and  thus  affords  the  possibility  of  adjusting  the  distance  between 
the  grinding  surfaces.  The  product  is  supplied  by  the  hopper  Q,  and  a 

tube  r  which  may  be  raised  and 
lowered  by  a  crank  mechanism  po 
driven  by  a  hand- wheel  n.  The 
oil  is  supplied  from  lubricator-box 
m  through  a  copper  pipe  t,  directed 
to  the  mill-bush.  From  the  mill- 
bush  it  is  conveyed  to  the  step- 
bearing  by  a  canal  i.  The 
step-bearing  and  the  mill-bush 
are  completely  isolated  from  dust. 
The  product  is  shovelled  from  the 
bottom  of  the  casing  into  the 
spout  Z  by  means  of  scrapers  s. 

In  comparing  the  two  designs 
of  stone  mills  and  attaching 
supreme  importance  to  ball  bear- 
ings, we  are  inclined  to  favour  engineer  Fuhrman's  design,  for  the 
assembling  of  a  ball  step-bearing  in  one  plane  presents  no  difficulties. 
In  Mr.  Panshin's  design,  the  fitting  up  has  to  be  done  in  two 
planes,  and  a  slight  inaccuracy  in  this  case  compels  one  to  work  but 
in  one  plane.  At  first  sight  the  three  rows  of  balls  in  Fuhrman's  step- 
bearing  also  present  inconveniences,  namely,  all  the  three  rings  of  balls 
are  evenly  loaded,  and  therefore  the  balls  of  the  outer  ring,  having  a  longer 
course  to  run,  ought  to  wear  out  more  rapidly.  It  has  to  be  taken  into 
consideration,  however,  that  the  number  of  balls  in  that  ring  is  greater, 
and  consequently  the  load  per  ball  is  less.  Thus  a  judicious  choice  of 
diameters  in  the  rings  of  the  three  rows  of  balls  will  equalise  the  wear  of 
the  balls. 

The  under-runner  stone  mills  with  ball-bearings  have  undoubtedly  a 


FIG.  175. 


CHA?.    IV] 


FLOUR   MILLING 


187 


good  future,  and  will  certainly  supplant  the  mills  of  the  ordinary  style 
with  an  upper  runner,  as  they  require  a  smaller  consumption  of  power, 
and  have  an  equal  capacity,  and  are  more  compact  than  the  common 
mills.  The  problem  of  the  rapid  wearing  of  balls  has  now  been 
completely  solved,  for  the  development  of  motor  car  production  has 
furnished  us  with  ball-bearings  more  durable  than  slide-bearings. 


4.  Stone  Mills — Vertical  (Horizontal  Axis  of  Rotation) 

While  studying  the  question  of  setting  the  working  surfaces  (p.  99, 
Fig.  90),  we  pointed  out  some  defects  of  the  vertically  set  surfaces,  and 


FIG.  176. 

will  therefore  not  discuss  them  now.  In  spite  of  those  defects,  the  mills 
with  vertically  mounted  stones,  rationally  designed,  owing  to  the  con- 
venience and  easiness  in  taking  them  to  pieces,  simplicity  of  attendance, 
and  their  compactness,  fulfil  their  purpose  successfully. 

"  Selecta  "  of  the  Works  of  form.  Seek  Bros.—"  Selecta  "  built  by 
the  Dresden  works  of  Seek  Bros.,  is  a  characteristic  construction  of 
stone  mills  having  a  horizontal  axis  of  rotation,  and  is  used  for  a  single 
grinding,  as  well  as  for  reducing  the  integuments  (Fig.  176). 


18B  FLOUR   MILLING  [CHAP,  iv 

In  a  cast-iron  casting  a,  easily  removed,  there  is  fixed  the  immov- 
able grinding  stone  b.  The  runner  b1is  set  in  the  left  section  al  of  the 
casing.  The  shaft  h  with  the  runner  set  on  it  by  means  of  a  cone  and  nut, 
rotates  in  three  bearings  with  ring  lubrications,  two  of  which  are  attached 
to  the  parts  a  and  a±  of  the  box.  The  third  bearing  is  set  on  a 
bracket. 

The  casing  a~a1  and  the  bracket  are  established  on  a  cast-iron  founda- 
tion-frame, and  riveted  to  it  by  bolts.  If  the  frame  is  correctly  placed 
on  the  foundation  or  on  the  floor,  the  correctness  of  the  position  of  the 
millstone  is  perfectly  guaranteed,  for  the  setting  of  the  bracket  and  the 
casing  aa:  is  done  accurately  at  the  works. 

The  throwing  of  the  stones  apart  and  together  is  performed  by  means 
of  a  lever  \  connected  by  an  eccentric  with  a  screw  ending  in  a  hand- 
wheel  /.  This  hand- wheel  serves  for 
a  more  accurate  adjustment  of  the 
distance  between  the  fixed  stone  b 
and  the  runner  fej.  This  is  done  in 
the  following  manner  :  the  shaft  h 
carrying  the  runner  6X  rests  on  a 
horizontal  pivot- journal  z,  which  is 
connected  with  the  box  p.  Into  this 
box  enters  a  screw  connected  with  a 
box  gv  which  rests  with  its  collars 
F  177  on  a  spring  set  in  between  the  hub 

of  the  box  and  the   casing   of    the 

bracket.  The  spring  will  resist  a  certain  normal  pressure.  By  turning 
the  hand- wheel  /  to  the  right  or  to  the  left,  one  may  accurately  regulate 
the  distance  between  the  grinding  surfaces.  But  when  a  big,  hard  object 
(nail,  nut,  &c.)  is  caught  in  between  them,  the  runner  presses  hard 
upon  the  shaft  h,  which  transmits  the  pressure  to  the  box  gr  Then 
the  spring  contracts  and  the  object  leaves  the  working  space  having 
caused  no  breakage,  while  the  runner  acted  upon  by  the  spring  returns  to 
its  former  position. 

The  slight  displacements  of  the  bed-stone  while  being  mounted  are 
likewise  provided  for.  This  is  done  in  the  following  way  :  in  the  right- 
hand  bottom  of  the  casing  a  containing  the  bed-stone,  there  are  set  four 
adjusting  screws  (only  one  is  visible  in  the  drawing,  they  are  seen  more 
clearly  in  the  general  view,  Fig.  177).  Through  the  bodies  of  the  screws 
there  pass  bolts  by  means  of  which  the  casing  of  the  bed -stone  can  be 
tightly  pressed  to  the  ends  of  the  adjusting  screws.  At  the  beginning 


CHAP,  iv]  FLOUR    MILLING  189 

the  grinders  are  adjusted  in  proportion  to  their  wear,  with  the  aid  of 
the  hand-wheel  /.  But  once  the  wear  of  the  working  surface  has 
reached  the  stage  when  the  turning  of  the  hand-wheel  becomes  purpose- 
less, then,  having  freed  the  bolts  and  screws  of  their  nuts,  the  fixed  stone 
is  pushed  together  with  its  casing  in  the  direction  of  the  runner,  the  hand- 
wheel  /  having  previously  been  brought  to  its  former  position.  The  fur- 
ther adjustment  is  performed  as  far  as  circumstances  permit,  again  by 
the  hand- wheel,  until  the  displacing  of  the  adjusting  screws  has  to  be 
renewed.  This  manipulation  is  repeated  so  long  as  the  length  of  the 
adjusting  screws  permits,  i.e.  until  these  screws  completely  sink  into  the 
hollow  of  the  casing  a. 

When  the  fixed  stone,  in  consequence  of  wear,  has  attained  the  last- 
mentioned  position,  the  runner  can  be  further  transposed.  To  this  end 
(Fig.  178),  the  adjusting  screws  I  are  screwed  out  of  the  casing  and  the 
runner,  keyed  on  to  the  shaft,  is  pushed  with  the  aid  of  a  cone-shaped 
entasis  i  to  the  right  towards  the  fixed  stone.  To 
assist  in  transposing  the  runner,  a  box  o  is  set  on  the 
shaft  and  the  runner  with  its  casing  is  shifted  more  to 
the  right.  During  the  operation  following  the  stones 
are  adjusted  in  the  manner  explained  above,  until  they 
are  totally  worn. 

In  dismounting  the  mill,  special  hoops  are  screwed 
on  to  the  frame,   and  after  the  bolts  coupling  both 
halves  at  and  a  have   been   loosened,  with  due  precautions  the  frame 
is  shifted  with  the  aid  of  rollers  over  the  hoops  to  the  right. 

This  mill  may  be  furnished  with  stones  of  various  types.  For  the 
purposes  of  aspiration  the  machine  is  either  included  in  the  general  aspira- 
tion, if  there  is  a  centrifugal  appliance,  or  provided  with  a  special  dust- 
collector.  During  the  ventilation  the  opening  in  the  left-hand  side 
section  of  the  casing  a^  usually  covered  with  wire  cloth,  is  hermetically 
stopped  up. 

The  feeding  appliance  consists  of  a  hopper  with  an  adjustable  bottom, 
similar  to  the  rocking  shoe  in  the  hopper  of  an  ordinary  stone  mill.  The 
hopper  is  driven  by  a  pulley  t  which  can  be  shifted  along  the  shaft  h. 
For  regulating  the  feed  there  is  a  distributing  slide  valve  by  means 
of  which  the  outlet  in  the  adjustable  bottom  may  be  enlarged  or  made 
smaller.  The  product  fed  into  the  millstone  slides  over  a  magnet  which 
extracts  all  pieces  of  iron,  and  is  then  conveyed  by  the  worm  n  to  the 
working  space  of  the  grinders. 

When  the  mill  is  in  operation  and  filled  with  product  the  lever  hl  set 


190 


FLOUR   MILLING 


[CHAP,  iv 


on  the  box  gr/is  brought  into  a  position  denned  by  the  pawl  of  the  ratchet 
wheel,  i.e.  it  is  turned  to  an  angle  of  90°  in  respect  to  its  former 
position.  Then  by  means  of  the  hand- wheel  /,  the  runner  is  brought 
by  the  screw  so  close  to  the  fixed  stone  as  to  produce  a  grist  of 
the  desirable  fineness.  If  the  process  has  to  be  quickly  stopped, 
it  is  sufficient  to  turn  the  lever  on  box  gl  back  the  90°  and  the 
stones  acted  upon  by  the  spring  will  move  apart.  At  the  same  time 
the  movement  of  the  rocking  shoe  must  be  stopped  with  the  aid  of  a 
disengaging  gear. 

If  any  hard  foreign  object  is  fed  into  the  mill  together  with  the  grain, 
the  runner  may  be  thrown  out  of  action  by  pressing  the  spring,  which 
forces  back  the  box  g1  and  the  adjusting  mechanism. 

This  set  may  be  furnished  with  quartzose  stones,  but  the  artificial 
emery  stones  are  preferable,  as  they  require  redressing  much  more  rarely. 
There  is  no  need  to  make  slanting  furrows  here,  it  is  sufficient  to  deepen 
the  ventilatory  furrows  from  time  to  time  and  smooth  the  spout  for  the 
ready  product. 

Of  stone  mills  of  this  type  Thos.  Robinson's  "  Dreadnought,"  the 
"  Monarch  "  of  Dobrovy  and  Nabholtz,  have  a  name,  as  have  the  mills 
of  a  similar  type  from  many  American  works,  whence  the  European 
engineers  have  borrowed  the  design. 

Below  are  given  the  data  of  the  capacities  of  all  three  types  of  stone 
mills  obtained  in  general  practice.  In  the  second  table,  D  denominates 
the  diameters  of  the  stones  in  quarters,1  n  the  number  of  revolutions, 
P  capacity  per  hour,  N  the  number  of  effective  horse-powers,  and  Q  the 
weight  of  the  mill  without  the  stones. 


TABLE    XVII 

THE  CAPACITY  OF  STONE  MILLS 
(1)  Upper-Runner  Mitts 


Diameter  of  Stones, 
in  Quarters.1 

Number  of 
Revolutions  per 
Minute. 

Number  of 
H.P.  required. 

Capacity  per  Hour, 
in  Bushels. 

Weight  of  Mill 
without  Stone, 
in  Lbs. 

f  (35  in.) 

160-170 

4-5 

6-8 

4140-4320 

f  (42  in.) 

145-155 

5-6 

8-10 

4500-4680 

I  (49  in.) 

135-145 

6-7 

10-14 

4860-5040 

f  (56  in.) 

120-130 

7-8 

14-16 

5120-5300 

Quarter =7  in.    "  Quarter  "Js  aTRussian  measure  used  in  measuring  millstones. 


CHAP.    IV] 


FLOUR    MILLING 


191 


(2)  Under-Ruuner  Mills  on  Balls 


D. 

n. 

P. 

N. 

Q. 

4  quarters 

180-200 

6-10 

3-5 

900-1080 

5    » 

170-180 

10-16 

5-10 

1260-1440 

r> 

145-150 

23-26 

10-15 

1730-1800 

7 

135-140 

30-35 

15-20 

2050-2780 

8 

120-125 

40-48 

20-25 

2780-2960 

(3)  Stone  Mills  of  the,  "  Selecta  "  Type 


Diameter  of  Stones 

Number  of 

Capacity  per  Hour, 
in  Bushels. 

Number 

I 

Full  Weight 

in  Millimetres 

Revolutions 

of 

of  Mill, 

and  Verschokes. 

per  Minute. 

H.P. 

in  Lbs. 

Coarse  Flour. 

Soft  Flour. 

256  mm.  =  5-Jv. 

1000-1200 

6-10 

2-6 

2-4 

396-432 

400    „     =  9   v. 

900-1000 

16-24 

8-14 

6-10 

828-900 

600    „     =13iv. 

750-800 

45-60 

20-25 

15-20 

1908-1980 

711    „     =16    v. 

700-750 

60-75 

25-32 

20-25 

2720-2512 

The  considerable  difference  in  the  weight  of  machinery  given  in  this 
table  should  be  taken  notice  of.  The  light  weight  of  the  under-runner 
mills  on  balls  and  sets  of  the  "  Selecta  "  type  in  comparison  to  the  upper- 
runner  mills  does  not  speak  in  favour  of  mills  of  the  old  type,  which  are, 
in  fact,  losing  ground  to  the  new  type  of  machinery,  owing  to  their 
cheapness  and  satisfactory  operation. 


5.  The  Capacity  and  Calculation  of  Stone  Mills 

On  examining  the  practical  data  of  the  capacity  of  stone  mills  with 
grinders  of  natural  and  artificial  stone,  we  see  that  it  does  not  exceed  1  to 
2  bushels  to  an  effective  horse-power. 

The  data  of  capacity  given  here  pertain  to  the  single  grinding,  and  have 
been  obtained  from  the  materials  of  large  works,  which  give  us  no  reason 
to  doubt  their  veracity.  Those  data  are  confirmed,  with  insignificant 
reductions,  by  our  immediate  observations.  The  reduced  capacity, 
however,  results  from  the  millstones  being  badly  attended  to  by  inex- 
perienced millers  rather  than  from  any  inaccuracy  in  the  data  given  by 


192 


FLOUR    MILLING 


[CHAP,  iv 


the  factories.  For  this  reason,  in  calculating  the  capacity  of  stone  mills 
it  ought  to  be  set  at  5  to  10  per  cent,  lower  than  as  per  catalogues  of  large 
firms  ;  it  is  still  better  to  employ  an  experienced  miller  able  to  handle 
the  machinery  well. 

Detailed  investigations  of  the  capacity  per  horse-power  per  hour  are 
published  by  Wiebe,1  and  are  based  upon  his  experiments  on  mills  in 
Budapest  (Pester  Miihlen).  These  researches,  in  spite  of  their  dating  from 
so  early  a  period,  have  not  lost  their  value  in  a  comparative  sense, 
owing  to  the  fact  that  the  standard  of  millstone  grinding  was  very 
high  at  the  time  mentioned.  The  stones,  the  capacity  of  which  was 
investigated,  were  5  feet  in  diameter,  and  ran  at  the  rate  of  120  r.p.m. 

Those  data  relate  to  the  plain  and  high  grinding  on  stones.  The 
first  figures  (belonging  to  plain  grinding)  approach  our  modern  data. 
If  they  are  rectified  in  proportion  to  the  increased  number  of  revolutions 
of  the  millstones  and  an  improved  ventilation,  108  Ibs.  per  horse-power- 
hour  will  be  a  perfectly  normal  capacity  for  modern  millstone  sets. 


TABLE  XVIII 

CAPACITY  PER  HORSE-POWER  (STEAM)  PER  HOUR  ACCORDING 

TO  WIEBE. 


WHEAT. 

Without 
Ventilation, 
Ibs. 

With 
Ventilation. 
Ibs. 

(1)  Single  grinding  with  a  regrind- 
ing  of  the  rest 
(2)  Grinding  in  two  passages  . 
(3)  Grinding  in  three  passages 

59-4 
50-4 
45-0 

58-3 
34-9 
28-4 

79-6 
67-3 
59-4 

78-8 
47*2 
37-1 

RYE. 

(1)  Grinding  in  a  single  passage 
(2)  Grinding  in  two  passages  . 
(3)  Grinding  in  three  passages 

In  passing  to  the  question  of  the  design  of  stone  mills,  it  must  be 
pointed  out  that  the  calculation  of  exact  details  of  this  machinery  de- 
pends on  the  weight  of  the  stones,  which,  in  its  turn,  is  determined  by 
the  force  necessary  to  crush  the  grain.  The  natural  stone,  being  diverse 
ajid  variable  in  its  structure,  does  not  allow  of  the  evolution  of  any 

1  Wiebe,  Die  Mahlmiihlen. 


CHAP,  iv]  FLOUR    MILLING  193 

analytical  formula  as  regards  the  normal  dimensions  or  for  the  velocity 
of  rotation  of  the  stones.  Owing  to  this  fact  we  must  have  recourse 
to  the  empiric  data  evolved  by  factories  and  mills  in  their  long  years 
of  practical  experience,  according  to  which  to  one  square  metre  of 
the  working  surface  700-1000  kilogrammes'  weight  of  the  runner 
is  accepted.  Availing  himself  of  those  data,  Navier  suggests  the  fol- 
lowing formula  for  the  weight  P  of  the  runner  :  P=668D2  kilogrammes, 
D  being  the  diameter  of  the  stone  in  metres.  If  the  height  h  of  the 
stone  is  to  be  determined,  then,  denominating  the  density  of  the  stone 
as  6,  the  diameter  of  the  stone  D,  the  diameter  of  the  eye  d,  we  obtain 
the  pressure  to  one  square  metre  of  the  working  surface  : 


for  the  weight  of  the  millstone  P=~ — - — —  (the  volume  of  thecylindric 

ring  multiplied  by  the  specific  gravity  of  the  stone),  while  — — ^ — '  is 

the  area  of  the  base  of  this  ring.  Seeing  that  the  density  8  of  the 
natural  stone  is  equal  to  2000,  and  taking  the  average  of  p  as  850  kilo- 
grammes, we  obtain  ^=0*425  metres,  which  closely  approaches  the 
dimensions  of  the  stones  made  by  French  manufacturers. 

Results  of  a  greater  accuracy  may  be  obtained  for  artificial  stones, 
as  the  uniformity  in  their  structure  enables  us  to  find  more  accurate 
limits  of  weight. 

As  regards  the  circumferential  velocity  of  the  millstones,  Wiebe 
proposes  9*42  metres  per  second  for  the  utmost  limits,  Fairbairn 
10  metres  per  second,  and  modern  constructors  place  the  highest  limit 
at  16  metres  per  second  for  good  French  stones. 

No  scientific  experimental  operations  with  the  view  to  calculating 
the  power  consumed  in  the  working  and  the  empty  run  of  the  stones  have 
been  made  as  yet,  while  the  imperfect  observations  give  the  following 
general  rule  :  it  is  considered  that  to  move  a  grinding  stone  a  force 
equal  to  -^  to  -^  of  the  weight  of  the  stone  is  required,  applicable  at  the 
distance  of  f  from  the  axis  of  rotation.  Then  the  work  T  per  second 
will  be  expressed  by  the  formula  : 

__P_     %nDn  _    P.nDn 
~~ 20-22  '  3  60        1800-1980 

where  D  is  the  diameter  of  the  stone,  n  the  number  of  revolutions  per 
minute.  General  practice  in  Russia  has  established  a  still  more  simple 

N 


194  FLOUR   MILLING  [CHAP,  iv 

rule,  according  to  which  one  H.P.  is  reckoned  to  each  quarter,  i.e.  28 
inches  require  four  H.P.,  35  inches  five  H.P.,  42  inches  six,  &c. 

In  calculating  the  consumption  of  power  of  the  stone  mills,  it  must 
be  kept  in  mind  that  the  power  consumption  depends  on  how  the  grinding 
is  done.  The  numbers  of  horse-power  given  above  are  to  be  regarded 
as  an  average. 

A  stone  mill  running  empty  consumes  20  to  25  per  cent,  of  power. 

Wiebe  offers  the  following  inference  for  the  definition  of  the  relation 
between  the  velocity  of  rotation  of  the  stone  and  the  consumption  of 
power  : 

Let  us  suppose  that  h  is  the  distance  between  the  working  surfaces 
at  the  inflow  of  the  product,  u  the  speed  at  which  the  product  is  dis- 
charged in  a  radial  direction.  The  volume  of  product  V  delivered  per 
second  will  be  equal  to  nDhu,  D  being  the  diameter  of  the  stones.  If 
we  grant,  with  a  great  approximation,  that  the  volume  of  the  reduced 
product  is  proportionate  to  the  volume  Q  flowing  into  the  mill,  then 
V=aQ,  where  a  is  the  coefficient  of  proportionality.  Reckoning  that 
the  speed  of  the  product  delivered  is  proportionate  to  the  circum- 
ferential velocity  of  the  grinder,  we  obtain  u=f$v,  where  v  is  the  velocity 
of  the  stone,  and  /?  the  coefficient  of  proportionality.  Substituting 
those  significations  in  the  formula  for  V,  we  shall  obtain  for  the  bulk 
discharged  per  second  : 

T7       ^     nDnnDKh       , 
V=aQ=  -      r    ,  whence 


Q 

~  =  ~7?7i 

60a 


By  substituting  the  mean  values  of  n  and  Q  in  this  formula,  we  shall 
define  this  constant  quantity.  The  following  problem  may  be  solved 
as  an  example.  Granted  D=l'5  metres.  The  number  of  revolutions 
n  =  120,  48  litres  of  wheat  per  one  horse-power  have  been  fed  in  per  hour. 
Then  per  minute  Q=0'S  N,  N  denominating  the  number  of  horse-power, 
Hence  (reckoning  Q  per  hour  to  be  equal  to  275  litres)  : 


Consequently,  N=D*n  .  0-019.     The  constant        -  may  be  regarded 

JLJ  Tl 

as  equal  to  0*02,  then  the  formula  defining  the  number  of  powers  will  be 

N=D2n  .  0-02. 

• 

But  seeing  that  the  capacity  of  the  stone  mills  in  modern  technics 
has  risen,  the  coefficient  0'02  should  be  slightly  increased, 


CHAP.    IV] 


FLOUR    MILLING 


195 


6.  Mills  with  Metal  Grinders 

Repeated  attempts  have  been  made  in  Europe  to  supplant  the  stone 
grinders  by  metal  ones — cast  iron  or  steel — but  no"  satisfactory  results 
have  been  obtained.  In  Europe,  chiefly  in  Germany,  up  to  this  day  such 
mills  are  made  only  for  laboratory  purposes.  The  American  technical 
science,  however,  has  evolved  a  series  of  splendid  designs  of  mills  with 
steel  grinders  for  industrial  purposes,  mainly  for  grinding  forage  products 
— maize,  barley,  oats,  cotton  seeds,  &c. 

The  Americans  build  mills  of  this  style  with  a  horizontal  axis  of 
rotation,  and  mostly  with  twin  rotating  grinders. 

Figs.  179  and  180  represent  a  universal  attrition   mill  "  Scientific  " 


FIG,  179. 

built  by  "  The  Food  Manufacturing  Co.,"  Springfield,  Ohio.  The  product 
is  fed  into  hopper  A  with  a  feeding  and  crushing  roller  4  with  pulley 
44  driven  from  a  special  shafting.  The  regulation  of  the  feed  is  per- 
formed by  a  cast-iron  valve  38  by  means  of  a  screw  39,  which  are  set 
apart  on  B.  If  whole  ears  of  maize  are  to  be  ground,  a  narrow  passage 
is  left  open  between  the  valve  and  the  side  of  the  hopper  :  should  the 
product  fed  in  be  the  grain  of  barley,  oats,  &c.,  the  valve  is  kept  almost 
quite  open.  From  the  hopper  the  product  streams  (arrows  s)  into  the 
working  space  through  the  eye  of  the  left-hand  stone. 

The  grinders  are  cast-iron  discs  28  and  33  with  cover  plates  32  of  hard 
tempered  steel  with  cutting  edges  (Fig.  180),     The  reduced  product  is 


196 


FLOUR   MILLING 


[CHAP,  iv 


discharged  as  pointed  by  arrows  slt  The  grinders  are  enclosed  in  a  cast- 
iron  built-up  casing  27.  The  shafts  of  the  grinders  are  set  each  on  two 
bearings  with  bronze  bushes  and  ring  lubrication  and  have  ball  step- 
bearings  9.  The  right-hand  grinder  has  a  tension  adjustment  drawn  in 


FIG.  180. 

detail  on  C,  which  is  arranged  as  follows  :  the  pivot  journal  of  the  shaft 
transmits  the  pressure  to  the  bolt  2,  which  in  its  turn  presses  upon  the 
cross-head  3  resting  with  its  ends  on  springs  48  ;  the  spring  and  the  ends 
of  the  cross-head  are  set  on  guides  49  fixed  to  the  frame  of  the  bearing. 
The  bolts  2  and  47  of  the  end  bearings  also  serve  for 
the  fitting  up.  For  lifting  and  inspecting  the  grind- 
ing surfaces  there  is  a  rack  and  pinion  52  operated 
by  a  ratchet  wheel  with  the  aid  of  a  lever  56.  One 
end  54  of  this  rack  is  connected  by  a  joint  to  the 
base  plate  on  which  the  bearings  are  set.  The 
bearings  and  the  casing  are  set  on  the  foundation 
frame.  The  accuracy  in  the  setting  of  the 
shafts  of  the  grinders  is  guaranteed  by  the  con- 
struction of  the  bearings,  which  may  be  raised  or  lowered  by 
bolts  a,  and  pushed  backwards  or  forwards  by  bolts  D  (see  general 
view). 

For  the  inspection  and  cleaning  of  the  grinders  the  casing  is  broken 
off,  the  belt  removed,  and  the  whole  side  with  the  tension  adjustment  is 
lifted  with  the  rack  and  pinion.  The  plate  20  of  this  side  is  placed  on 


FIG.  181. 


CHAP,  iv  ] 


FLOUR   MILLING 


197 


the  base  plate  free  and  is  not  bolted  to  it ;  while  the  plate  of  the  other 
side  is  cast  in  one  block  with  the  base  plate. 

By  the  first  bearing  on  the  left  (section)  a  collar  63  is  set,  and 
the  bush  of  the  pulley  22  serves  as  guard  for  the  shaft  of  right-hand 
grinder.  The  holes  E-E  in  the  frame  are  made  for  the  belts  to  pass 
through. 

This  machine  has  been  rationally  designed,  and  its  sole  defect  is  the 
absence  of  ventilation,  which  is  particularly  important  for  cooling,  when 
hard  mineral  substances  are  ground.  The  worn  grinding  steel  discs 
(Fig.  181)  are  easily  replaced  by  new  ones.  The  capacity  of  the  machines 
of  this  type  and  the  power  consumption  are  given  in  the  following 
table  : 

TABLE  XIX 

CAPACITY  or  MILLS  WITH  METAL  GRINDING  Discs 


Diameter  of 
Grinding  Discs. 

Number  of 
Revolutions. 

Capacity  per 
Hour, 
in  Bushels. 

Number  of 
H.P. 

General 
Weight, 
in  Lbs. 

16  inch. 

2000 

14-18 

10-12 

1800 

19     „ 

1900 

25-45 

15-18 

1800 

22     „ 

1800 

35-50 

20-25 

2100 

24     „ 

1700 

70-110 

25-30 

2100 

26     „ 

1450 

90-125 

25-35 

3950 

30     „ 

1350 

125-165 

35-45 

4740 

36     „ 

1200 

145-185 

45-60 

5950 

This  table  gives  us  the  produce  of  feed,  this  type  of  mills  not  being 
employed  for  milling  flour  for  human  consumption,  because  the  energetic 
activity  of  the  cutting  discs  reduces  to  powder  the  bran  too,  which  cannot 
be  extracted  from  the  meal. 

Lately  in  the  West  European  countries  the  use  of  mills  with  steel 
grinding  plates  also  for  other  kinds  of  grinding  has  begun  rapidly  to 
spread.  These  machines  have  also  appeared  in  Russia.  The  absence  of 
any  definite  data  in  general  practice,  however,  allows  us  to  utter  no 
positive  opinion  concerning  them.  As  to  the  firms  selling  them,  they  give 
but  advertisements.  At  any  rate,  owing  to  the  cheapness  of  these  mills 
and  the  simplicity  in  attending  to  them,  they  may  play  a  considerable 
role  in  supplanting  the  heavy  machinery  on  the  peasantry  market. 

The  grinding  discs  constitute  an  essential  detail  of  this  machinery. 
Fig.  182  represents  two  kinds  of  those  discs.  One  has  the  cutting  facets 
arranged  after  the  type  of  the  circular  furrows,  the  other  is  with  figure 


198  FLOUR   MILLING  [CHAP,  iv 

rim  collars  A  and  radial  edges  B  at  the  outlet  of  the  product.     Undoubt- 
edly the  first  design  of  the  facets  is  more  rational  than  the  second.     In 


FIG.  182. 

the  discs,  the  heads  of  the  bolts  riveting  them  to  the  millstones  rest  in 
square  sockets  D  of  a  sufficient  depth  for  the  heads  to  be  sunk  to  a  level 
with  the  working  surface  of  the  disc. 

IV 

MACHINES  ACTING  BY  IMPACT 

The  machines  acting  by  impact  are  constructed  on  the  principle  of 
transforming  the  kinetic  energy  into  a  crushing  action,  which  is  the  result 
of  pressing  a  body  beyond  the  elastic  limits. 

Supposing  we  have  a  body  weighing  P  kilogrammes  for  the  crushing 
of  which  work  equal  to  E  kilogram  meters  is  required.  Then,  reckoning 
the  initial  velocity  of  motion  of  the  body  to  be  equal  to  zero,  we  obtain 
the  following  formula  for  the  destructive  work  : 


p 

As  — =m,  herefrom  is  defined  the  velocity  v  of  motion  of  the  striking 

element  or  the  velocity  of  the  body,  with  which  it  must  hit  against  an 
immobile  object,  to  be  destroyed  : 

J2E 

v=\j  — 
7  ra 

It  the  hitting  element  and  the  body  to  be  broken  are  moving  towards 
each  other  and  the  velocities  corresponding  to  their  motions  are  Fx  and  F2 
the  resulting  velocity  will  be  Fx+  F2. 

Disintegrators. — One  of  the  first  machines  of  this  type  (Fig.  183)  was 
suggested  by  Carr.  The  working  organs  in  this  machine  are  iron  discs  A 
and  J5,  with  steel  taper-pins  a  and  6  set  in  concentric  circles.  Both  the 
discs  are  brought  into  rotatory  motion  in  opposite  directions  by  means  of 


CHAP.    IV] 


FLOUR   MILLING 


199 


belt  pulleys  E  and  E^  The  disc  A  on  the  left-hand  side  is  attached  to  the 
bush  A!  with  taper-pins  e.  The  cast-iron  casting  H  encloses  both  discs. 
The  tube  G  which  conveys  the  grain  to  the  working  space  on  receiving  it 
from  the  tank  F  and  hopper  JV,  likewise  passes  through  that  casing. 
Speaking  generally,  the  design  of  this  machine  greatly  reminds  one  of 
the  American  grinding  machines  of  the  "  Scientific "  type,  differing 
from  them  in  the  character  of  action  performed  by  the  working  surfaces. 

The  grain  falling  on  the  moving  taper-pins  receives  an  impact,  is 
rejected,  and  meets  the  next  pin,  which  again  strikes  it.  In  this  manner 
the  product  travels  in  a  zigzag  line  to  the  outlet,  being  gradually  reduced. 

Though  the  disintegrators  are  mentioned  in  catalogues  of  some  fac- 


FIG.  183. 

tories,  they  cannot  be  recommended  for  milling,  for  they  do  not  work 
economically,  and  require  a  great  quantity  of  power.  For  instance,  the 
disintegrator  that  worked  at  the  exhibition  in  Paris  (1878)  expended  some 
30  horse-power  yielding  about  1800  Ib.  per  hour,  i.e.  60  Ib.  per  hour  power. 
This  was  on  the  average  15  to  20  per  cent,  below  the  capacity  of  the 
stone  mills  of  the  time. 

The  dimensions  of  the  working  parts  of  those  machines  were  generally 
the  following  :  the  diameters  of  the  discs  were  350  to  1800  mm.,  the 
diameters  of  the  taper-pins  10  mm.,  their  length  and  the  distance  between 
the  discs  almost  the  same,  230  to  280  mm.,  the  number  of  revolutions 
1200  to  400. 

The  Nagel  and  Kamp's  disintegrator  (Fig.  184)  differs  from  the  one 
preceding,  one  of  its  discs  A  being  stationary.  This  machine  serves  for 
the  further  reduction  of  the  product  obtained  after  passing  the  grain 


200 


FLOUR   MILLING 


[CHAP,  iv 


once  or  twice  through  the  roller  mills.  On  leaving  the  roller  mill  the 
semolina  passes  into  the  hopper  1,  whence  by  a  feeding  roller  H  it  is 
delivered  into  the  working  space.  In  this  machine  the  constructor  tried 


FIG.  184. 

to  obviate  the  ventilating  effect  of  the  disintegrator, '  which  results  in 
pulverisation  of  the  meal ;  this  explains  the  presence  of  the  stuffing 
boxes  2  and  3. 

The  disproportionately  large  cisterns  D  and  Dt  serve  to  collect  the 

exhaust  oil  and  drain  it 
through  cocks  i.  T  is  the  driven 
belt-pulley,  while  the  loose  belt- 
pulley  J  is  the  tightener. 

To  get  a  clear  idea  of  the 
process    of    movement    of  the 
product  over  the  working  area 
in  a  machine  of  the  first  type, 
let    us    suppose    we    have    it 
(Fig.  185)  in  section  over  the 
taper  -  pins     parallel     to     the 
discs.     The  pins   P15   P3,   and 
and    the   direction    of    the    pins 
The  angular  velocity  of  rotation 


P5  are   moving    in    the    direction   8, 

P2  and  P4  is  pointed  by  the  arrow  St. 

of  the  two  discs  is  co,  then  the  velocity  of  the  pins  is  rjw,  r2w,  &c.     The 

berry  A  falling  through  the  eye  of  the  disc  encounters  the  pin  P15  which 

throws  it  with  an  impact  at  tangent  at  with  the  speed  r^o.     On  its  way 


CHAP,  iv]  FLOUH  MILLING  201 

the  berry  meets  the  pin  P2  of  the  second  disc  and  is  rejected  at  a  tangent 
line  a  2  to  the  pin  P3  moving  in  a  contrary  direction,  with  the  velocity 
r2a).  At  the  moment  the  grain  and  the  pin  P2  meet,  the  velocity  of  the 
impact  is  equal  to  r^-^r^a}  cos  a15  for  the  velocity  of  the  pin  P2  is  pro- 
jected upon  the  direction  of  the  motion  al5  by  the  quantity  r2w  cos  ar 
With  a  slight  inaccuracy,  however,  we  may  mark  rl=r2  cos  c^.  Sub- 
stituting the  r2  of  this  equation  into  the  formula  of  the  velocity  of  the 
impact,  we  obtain  : 

F1=2r1co. 

By  reasoning  in  the  same  manner  with  regard  to  the  percussion  of  the 
grain  or  its  particle  by  the  taper-pins  P3,  P4,  P5  .  .  .,  we  shall  accordingly 
obtain  the  velocities  : 

F2=2r2co 

F3=2r3o> 

F4=2r4a>,  &c. 

If  we  mark  the  distance  in  a  radial  line  between  the  pins  Pl3  P2,  P3, 
&c.,  through  n,  the  result  will  be  : 

F1=2r1co 


,,  &c., 

which  means  that  the  velocities  of  the  impact  accelerate  in  proportion 
to  the  product's  approach  to  the  outlet  in  arithmetic  progression,  the 
denominator  of  which  is  2nw.  In  accordance  with  it  increases  the  force 
of  the  impact. 

This  conclusion  is  arrived  at  on  the  supposition  that  in  every 
element  of  the  route  n  to  the  outlet,  the  product  encounters  taper- 
pins  of  the  forward  and  backward  motion  of  the  discs.  Other, 
often  occurring  cases,  when  the  product  encounters  the  pins  of  the 
retrograde  motion  only  on  its  2n  way,  are  also  possible.  Then  the 
law  of  acceleration  of  the  velocities  in  arithmetic  progression  is 
infringed. 

If  the  law  we  deduced  respecting  velocities  were  not  infringed  through 
the  blowrs  of  some  of  the  pins  being  missed,  then,  the  calculation  of  the 
number  of  revolutions  of  the  discs  being  correct,  and  the  distance  n 
definite,  the  grain  would  gradually  be  reduced  and  leave  the  working 
space  in  the  shape  of  a  product  uniform  in  size. 

In  reality,  however,  those  omissions  do  occur,  and  Wyngaert's  experi- 


202  FLOUR    MILLING  [CHAP,  iv 

ments  have  shown  the  following  results  of  grinding  on  a  disintegrator 
of  Carr's  type  : 

Flour 33  per  cent. 

Fine  middlings    .          .          .          .         .          .  20       „ 

Semolina    .          .          .  .          .         ..  14       „ 

Coarse  middlings          .          .          .          .          .  31       „ 

Offal.  2 


Total 


FIG.  186. 


.    100  per  cent. 

Thus,  after  a  passage  through  the  disintegrator,  66  per  cent,  of  the 
product  needs  further  treatment. 

Before  giving  a  definite  estimation  of  this  machine  we  shall  examine 

the  action  of  the  Nagel  and 
Kamp's  type  of  disintegrator,  i.e. 
with  one  rotating  disc. 

The  disc  with  taper-pins  Tlt 
T2)  T3  .  .  .  rotates  as  indicated 
by  arrow  8.  The  grain,  struck 
by  the  pin  Tl  (Fig.  186),  moves  in 
the  direction  a  t.  On  encountering 
on  its  way  the  fixed  pin  T2,  the 
grain  is  crushed  and  loses  its 
velocity  r^.  If  the  grain  does 

not  break,  still,  owing  to  its  insignificant  elasticity  when  compared  to 
the  steel  pin,  it  loses  its  velocity. 

We  suppose  in  the  first,  as  well  as  in  the  second,  case  that  it  will  not 
rebound  from  the  fixed  pin,  having  lost  its  velocity,  and  will  drop  in  the 
direction  a2  influenced  by  its  gravity.  Therefore,  the  pin  T3  will  give  it 
the  direction  aB.  In  this  wise  the  way  of  the  product  will  he  a1?  a2,  a3, 
a4,  a5,  .  .  .  Seeing  that  the  speed  of  the  free  drop  is  quite  insignificant 
in  comparison  to  the  velocity  of  the  pins,  we  may  ignore  the  item  of  the 
speed  down  a2  to  as.  Consequently,  the  velocities  of  the  impact  Tlt  T2, 
&c.,  will  accordingly  be  : 

Yl=r1co,  V3=r3co,  F5=r5o>,  &c. 
Let  us  compare  these  velocities  with  those  of  the  first  case  : 


Fa=2(ri:f  2 


Thence  it  is  clear  that  the  homonymous  impacts  in  the  first  case  have 
doubled  the  velocity  of  those  of  the  second.     This  means  that  to  attain 


CHAP,  iv]  FLOUR   MILLING  203 

the  crushing  effect  it  is  necessary  to  double  the  speed  of  rotation  of  the 
discs  in  the  disintegrators  of  the  second  type. 

In  drawing  this  inference,  we  rested  upon  the  supposition  that  the 
grain  or  a  particle  of  it  loses  its  speed  in  striking  the  fixed  taper-pins* 
thus  simplifying  the  problem  considerably.  But  it  may  be  maintained  that 
the  product  possesses  a  certain  elasticity,  and  on  striking  the  pin  T2  will 
rebound  in  compliance  with  the  law  of  percussion  of  elastic  bodies,  the 
mass  of  one  of  which  (the  pin)  is  infinitely  great.  Then  the  resultant 
velocity  of  the  impact  of  the  pin  T%  and  of  the  grain  will  be  greater 
than  in  our  preceding  inference.  The  process,  probably,  is  performed  in 
this  manner,  because  for  crushing  the  product  a  velocity  less  than  the 
double  velocity  required  in  the  first  case  suffices,  as  we  see  in  general 
practice  and  in  the  factory  data.  At  any  rate,  the  resultant  velocity  of 
the  blow,  conditionally  denominated  here  as  the  total  sum  of  velocities  in 
the  direction  the  grain  is  travelling,  needed  for  breaking  the  grain,  attains 
150  metres  per  second. 

Similarly  to  the  first  case,  we  have  been  examining  the  disintegrator 
of  the  second  type  operating  in  ideal  conditions,  supposing  that  the  pro- 
duct is  subjected  to  impacts  from  pins  of  each  row.  This  is  close  to  the 
fact ;  however,  gaps  in  the  series  of  blows  are  possible.  Altogether  the 
phenomenon  of  the  impacts  here  is  extremely  complicated,  and  the  char- 
acter of  the  process  may  be  judged  of  only  by  the  final  product,  as  it  is 
an  absolute  impossibility  to  observe  its  movements  in  the  working  space. 

The  grist  from  the  disintegrator  of  the  second  type  is  likewise  not 
uniform,  and  requires  further  treatment. 

We  shall  now  proceed  to  estimate  these  machines.  First  of  all,  the 
grist  yielded  not  being  uniform,  these  machines  cannot  be  used  inde- 
pendently, but  only  in  a  cycle  of  other  grinding  machinery.  For  a 
primary  breaking  of  the  grain  also  they  cannot  be  employed,  because  the 
meal  is  rendered  impure  by  an  admixture  of  bran.  It  was  attempted, 
therefore,  to  employ  them  for  grinding  the  grain  bruised  along  the  crease 
and  for  semolina.  But  even  here  there  is  no  reason  to  use  them,  for  they 
are  exceedingly  uneconomical.  Experiments  have  proved  that  the  energy 
expended  in  an  empty  run  amounts  to  44  per  cent,  of  the  total  power, 
whereas  the  millstones  require  a  maximum  of  25  per  cent. 

Attempts  have  been  made  lately  to  use  the  disintegrator  for  separat- 
ing the  particles  of  endosperm  from  the  offal,  after  the  third  or  fourth 
passage.  However,  these  attempts  we  also  consider  to  be  useless,  for  the 
machine  will  grind  the  good  semolina  and  admix  bran  to  the  meal  ob- 
tained. These  attempts  have  been  made  in  high  rye  milling. 


204  FLOUR   MILLING  [CHAP,  iv 

Lastly,  if  the  disintegrators  were  to  produce  results  of  as  high  a 
quality  as  those  obtained  from  other  milling  machines,  even  in  that  case 
they  would  not  be  worth  employing,  for  the  capacity  of  a  disintegrator  per 
horse-power  per  hour  is  considerably  below  that  of  other  machines.  Gener- 
ally speaking,  the  machines  acting  on  the  principle  of  a  blow  consume 
a  great  quantity  of  kinetic  energy  unproductively,  and  if  there  is  any 
possibility  of  replacing  them  by  others,  the  use  of  them  should  be  avoided. 
This  question  of  disintegrators  has  been  raised  in  our  manual  only  with 
a  view  to  making  an  end  of  them  once  and  for  ever,  and  to  warn  the 
engineers  against  losing  time  in  perfecting  the  designs  of  machines  of  the 
impact  type. 


**  MILLING  MACHINES  HAVING  THE  Axis  OF  ROTATION  OF  THE 
WORKING  ORGANS  IN  DIFFERENT  PLANES 

Our  examination  of  the  machines  of  repeated  action  has  shown  that 
these  machines  have  a  common  axis  of  rotation,  if  both  the  surfaces  have 
a  gyratory  motion  ;  if,  on  the  other  hand,  one  of  them  is  fixed,  its  axis 
of  symmetry  coincides  with  the  axis  of  rotation  of  the  other. 

Passing  now  to  machines  in  which  the  stock  is  treated  by  the  work- 
ing organs  but  once,  it  must  be  noted  in  the  first  place  that  their  axes 
of  rotation  lie  in  different  planes.  Speaking,  next,  of  the  form  of  the 
working  surfaces,  we  can  accept  only  planes  and  cylinders,  because 
other  rotatory  bodies  (cone,  hyperboloid,  &c.)  cannot  produce  equal 
circular  velocities  of  rotation  along  the  line  of  the  treatment  of  the  pro- 
duct ;  under  such  conditions  of  work,  therefore,  the  product  ground  will 
not  be  uniform  and  the  wear  of  the  working  surfaces  will  be  unequal. 

Taking  these  circumstances  into  consideration,  general  practice  and 
theory  have  produced  three  combinations  of  working  surfaces  (Fig.  187). 
The  first  of  them  (/)  is  a  cylinder  A  and  plane  B.  In  practice  we  know 
but  one  type  of  machinery  of  the  /  combination,  the  runner  (Fig.  188) 
employed  in  oil-manufacturing.  The  second  combination  (//)  is  two 
cylindric  surfaces  with  an  inner  contact,  and  lastly,  the  third  (///),  two 
cylindric  surfaces  with  an  outer  contact. 

In  all  those  combinations  the  working  surface  is  theoretically  defined 
as  a  straight  line,  and  therefore  the  product  is  considered  to  be  treated 
only  once  by  the  working  surfaces.  The  machines  of  the  runner  type 
differ  from  the  single  action  machines,  for  the  rotating  surface  B  carries 


CHAP.    IV] 


FLOUR    MILLING 


205 


the  product  under  treatment  several  times  to  A.  We  shall  not  occupy 
our  attention  with  machines  of  that  type,  as  they  are  in  no  way  connected 
with  flour  milling.  The  machines  of  the  second  type  are  used  for  grind- 
ing hard  substances,  for  instance,  gravel  for  artificial  millstones.  For 
this  reason  we  shall  later  on  give  a  description  of  a  typical  machine  of 
that  kind. 

The  third  combination  (///),  two  cylindric  surfaces  with  an  outer 
contact,  revolving  with  different  velocities,  is  the  basis  of  construction 
of  the  roller  mill,  the  most  widely  used  grinding  machine. 

In  studying  the  designs  of  machines  subjecting  the  product  to  a 
simple  treatment,  we  notice  that  their  working  organs,  very  rarely,  have 
equal  velocities  (runner),  or  the  speed  of  one  of  the  surfaces  equals 
zero  (//).  Usually,  however,  the  velocities  of  rotation  are  different,  as 
shown  in  combination  ///.  In  that  case  the  surface  B2  brings  the 
product  up  to  the  surface  A2,  which  performs  the  cutting  or  chipping 


FIG.  187. 


FIG.  188. 


action.  Of  the  degrees  of  velocities  we  shall  speak  below,  and  point 
out  now  that,  owing  to  their  variety,  the  product  undergoes  several 
cutting  or  chipping  operations  before  being  discharged  from  the  working 
space. 

We  shall  now  proceed  to  give  a  description  of  the  designs  of  these 
machines,  and  commence  with  a  type  of  the  second  (//)  combination. 

The  Mill  "  Griffin."— The  single  roUer  miU  "Griffin"  (Bradley 
Pulveriser  Co.)  shown  on  Figs.  189  and  190  is  an  original  type  of  a 
grinding  apparatus  for  hard  materials  such  as  cement  clinker,  Thomas' 
scoria,  superphosphates,  &c. 

Its  principle  of  operation  consists  in  crushing  and  grinding  the 
material  by  a  roller,  which  runs  over  the  casing  and  thus  acquires  a 
centrifugal  power. 

This  is  attained  by  means  of  the  following  construction  : 

On  a  cast-iron  base  plate  24,  in  shoes  66,  which  rests  on  rubber  buffers, 
there  are  set  timber  stands  23,  supporting  a  belt-pulley  frame  4. 

This  frame  is  of  cast  iron,  and  consists  of  two  box-shaped  parts  riveted 


206 


FLOUR    MILLING 


[CHAP,  iv 


together  by  two  bolts  63  below  and  joined  by  a  cross-piece  22  at  the 
top.  By  means  of  four  iron  rods  5  it  is  supported  in  a  correct  position 
in  respect  to  the  foundation.  With  their  upper  ends  those  rods  are 
screwed  into  the  frame  4,  while  the  lower  ends  run  through  bolt-holes 
in  the  corners  of  the  foundation  and  are  screwed  up  by  nuts,  under  which 
are  laid  two  rubber  buffers  64  apiece,  separated  by  an  iron  lining. 

The  first  machines  of  this  type,  however,  were  furnished  with  cast- 


23 


iron  stands,  but  the  vibration  of  the  casing  during  the  grinding  process 
was  communicated,  it  appears,  by  the  rigid  stand  to  the  frame,  and  had  a 
detrimental  effect  upon  the  bearings.  The  necessity  of  obviating  this 
vibration  has  led  to  the  above-mentioned  construction  of  an  elastic 
junction  between  the  frame  and  the  foundation. 

In  the  frame  4  there  are  set  a  fast  belt-pulley  17  and  an  auxiliary 
one  14.  The  latter,  by  means  of  the  belt-pulley  40  set  on  the  axle  41 
and  carrying  the  gear  60,  turns  the  worm  49  of  the  feeding  apparatus 


CHAP.    IV] 


FLOUR   MILLING 


207 


with  the  aid  of  the  worm  wheel  61.  The  fast  belt-pulley  17  rotates 
in  the  step-bearing  20  which  is  adjusted  by  means  of  bolts  37.  On  the 
inside  of  the  fast  belt-pulley  the  shaft  of  the  roller  1  is  suspended  on  a 
universal  joint  9.  The  joint  consists  of  a  ball  9  provided  with  journals  : 
the  latter  operate  in  bearings  which  slide  in  suitable  slots  of  the  belt- 
pulley  coupling.  On  the  lower  end  of  the  shaft  1  is  set  the  roller  2 


FIG.  190. 

furnished  with  a  change  ring  31.  Owing  to  a  drop-hanger  frame  inside 
it,  the  joint  can  swing  in  the  cup  24  in  all  directions.  The  cup  or  base 
24  carries  a  casting  70  on  which  the  roller  runs  ;  the  grinding  is  thus 
performed  between  them.  Owing  to  the  difference  in  the  diameter  at 
the  top  and  at  the  bottom  of  the  ring,  its  velocities  in  relation  to  the 
casing  in  the  generating  circle  are  unequal,  which  causes  the  reduction 
of  the  product  under  treatment. 

Round  the  casing  outside  there  are  several  slightly  oblong  apertures, 


208  FLOUR   MILLING  [CHAP,  iv 

through  which  the  product  falls  into  a  funnel-shaped  chamber  under 
the  cup,  whence  it  is  removed  by  a  transporting  appliance  (a  worm,  in 
Fig.  190). 

On  the  foundation  is  fixed  a  sieve  38,  a  cylindric  cone  45  surrounds  it 
covered  with  a  lid  44  carrying  a  cone-shaped  casing  25,  through  which 
the  shaft  1  passes. 

In  Fig.  190,  above  the  roller  are  seen  the  wings  of  the  fan  6,  which 
are  designed  to  propel  the  triturated  product  through  the  sieve  38. 

Under  the  roller,  and  attached  to  it  by  nuts,  there  are  the  wings  8 
for  stirring  the  product. 

There  are  no  moving  parts  in  the  dusty  atmosphere  of  the  cup. 
The  joint  in  the  belt-pulley  is  hermetically  covered  with  a  lid  13.  The 
lubrication  of  all  moving  parts  is  done  through  the  hole  12  drilled  in  the 
spindle  fixed  in  the  cross-piece  22. 

The  spindle  centres  the  lid  aided  by  cannon  steel  bush  27. 

The  dimensions  of  the  machines  are  the  following  : 

Height  above  the  foundation          ....     2600  mm. 

Size  of  the  base  plate 2100  X  1600  mm. 

Height  of  the  middle  of  the  belt-pulley  above  the 

foundation  ......     2045  mm. 

Diameter  of  the  belt-pulley  V         .          .          .       760mm. 

Number  of  revolutions  per  minute  .          .          .       200  mm. 

Consumption  of  work  .          .      between  15  and  25  powers 

Weight  of  the  whole  mill 10800  Ib. 

Diameter  of  the  roller  .....         460-470  mm. 
Diameter  of  the  casing  .....       760  mm. 

Length  of  the  generating  circle       .          .          .          .150  mm. 

Weight  of  the  casing ,          285  Ib. 

Weight  of  the  change  ring  of  the  roller  .          .         *  145  Ib. 

According  to  the  data  of  the  factory,  the  mill  reduces  to  fine  meal 
from  264  to  6400  cells  to  a  square  centimetre  of  the  sieve  between  1*5 
and  2  tons  per  hour  of  hard,  up  to  3.5  of  soft  phosphate,  and  from  1*5 
to  2*5  tons  of  Portland  cement,  quartz,  or  ore,  depending  on  the  hard- 
ness and  the  largeness  desired  of  the  product. 

The  machine  operates  in  the  following  manner  :  when  brought  into 
motion,  the  roller  rotates  in  the  same  direction  with  the  belt-pulley, 
and  on  reaching  its  normal  number  of  revolutions  is  jerked  out  of  its 
central  position  by  hand. 

The  centrifugal  force,  which  attains  3000  kilogrammes  when  at  full 
speed,  presses  the  roller  to  the  casting. 


CHAP,  iv]  FLOUR    MILLING  209 

Now  the  roller  commences  to  revolve  around  the  casing,  moving  in 
the  direction  opposite  to  the  one  it  started  with. 

The  product  is  poured  into  the  hopper  50. 

As  soon  as  there  has  collected  enough  material  in  the  cup  to  be 
scooped  up  by  the  wings  8,  it  is  flung  by  them  on  the  casing  and  the 
milling  commences. 

While  in  full  operation  the  contents  of  the  cup  are  stirred  by  the 
roller,  and  when  reduced  are  bolted  through  the  sieve  by  the  paddles  6 
which  do  the  duty  of  a  fan  at  the  same  time.  The  pieces  remaining 
unsifted  fall  back  under  the  roller. 

The  paddles  on  the  axis  of  the  roller  in  revolving  draw  the  air  in 
through  the  conic  casing  and  impel  it  through  the  sieve,  so  that  the 
dust  does  not  escape  outside. 

The  sieve  chosen  is  slightly  larger  than  the  final  product,  to  avoid 
choking  up. 

In  spite  of  the  ingenuity  of  the  design  described,  its  considerable 
complexity  must  be  pointed  out,  as  well  as  the  circumstance  that  a  large 
part  of  the  work  in  grinding  goes  to  overcome  the  resistance  offered  to  the 
motion  by  the  wings  8  and  the  continuous  stirring  of  the  heavy  product. 

The  application  of  rubber  buffers  also  cannot  be  regarded  as  a  happy 
thought,  for  india-rubber  exposed  to  the  open  air  rapidly  loses  its  elasticity 
and  will  do  so  the  quicker  because  of  the  vibration.  Steel  plate  springs 
would  serve  that  purpose  with  success. 

Then,  if  the  action  of  the  fan  be  regular,  the  dust  may  fly  out  of 
the  hopper  50  if  there  is  no  product  in  it,  and  therefore  a  lid  to  the  hopper 
would  be  an  acceptable  device. 

Lastly,  our  attention  is  drawn  to  the  unsheltered  position  of  the  feed- 
worm  49  set  on  the  free  end  of  the  shaft,  if  anything  large  were  to  fall  into  it. 

This  defect  could  likewise  be  obviated  by  carrying  the  bearing  53 
over  to  the  left,  behind  the  hoppers. 


VI 

ROLLER  MILLS 
1.  Conditions  of  Reduction  of  the  Product 

Before  we  direct  our  attention  to  the  construction  of  roller  mills, 
it  is  necessary  to  become  acquainted  with  the  character  of  action  of  the 
working  surfaces  and  the  conditions  under  which  the  reduction  of  the 
stock  is  possible, 

0 


210 


FLOUR   MILLING 


[CHAP,  iv 


We  have  (Fig.  191)  two  cylindric  surfaces  0  and  Ol  rotating  at  differ- 
ent velocities  in  the  directions  8  and  St.  At  a  certain  moment  there  is  a 
berry  (or  a  particle  of  one)  A  in  between  them,  which  is  to  pass  through 
the  working  space.  The  surfaces  of  the  cylinders  may  be  either  smooth 
or  consist  of  a  series  of  chisels  spoken  of  on  p.  153,  Fig.  135.  In  that  case 
the  rolls  are  said  to  be  corrugated  or  grooved,  and  the  product  may 

be  impelled  into  the  working 
space  by  their  corrugations  in 
any  combination  of  velocities 
and  diameters  of  rollers.  As 
to  the  operation  of  smooth 
rolls,  the  conditions  of  work- 
ing will  be  deduced  from  the 
following  considerations : 
First,  the  working  surfaces  and  the  product  under  treatment  must 
have  a  certain  coefficient  of  friction  /.  If  the  material  of  the  rolls  gives 
a  very  small  coefficient,  the  grain  A  will  not  be  drawn  into  the  work- 
ing space,  but  will  remain  sliding  above  it.  But,  as  the  working  surfaces 
are  prepared  of  a  definite  kind  of  material  (cast  iron  and  porcelain),  /  is 
likewise  a  definite  quantity.  Therefore  the  definite  /  has  to  be  combined 
with  other  elements  characterising  the  working  surfaces. 

For  the  coefficients  of  friction  /  and  the  angle  of  friction  y  Kick  gives 
the  following  quantities  : 

TABLE    XX 


FIG.  191. 


Material  of  Rollers. 

For  Fine  Middlings. 

For  Semolina. 

* 

/• 

f. 

/. 

Cast  iron  smooth,  polished 
Dead  cast  iron 
Cast  iron  used            .       ;.' 

Porcelain       '"••'.  -..       .          . 
• 

12° 

16° 

18° 

22° 

0-213 

0-287 
0-325 
0-404 

11° 

15° 
17° 

20° 

0-194 
0-268 
0-300 
0-364 

Let  us  examine  now  the  conditions  needed  for  the  product  to  be 
drawn  into  the  working  space  with  the  quantities  <p  and  /  given. 

The  rolls  being  in  rotation,  the  grain  A  weighs  upon  their  surfaces  in 
the  points  of  contact  n.  Suppose  the  reactions  of  that  pressure  to  be  p, 
their  direction  is  evidently  radial.  Then  the  forces  of  friction,  directed 
in  tangents  at  the  points  of  contact  of  the  rolls  and  the  product,  will  be  fp. 
If  the  angle  of  direction  of  the  reactions  and  of  the  centre  lines,  named  the 


CHAP,  iv]  FLOUR   MILLING  211 

angle  of  grasping,  is  a,  then  the  resultant  of  the  two  fp,  which  is  the  force 
drawing  the  product  into  the  working  space,  will  be  2fp  cos  a. 

To  bring  about  this  drawing  in  of  the  product  it  is  necessary  that 
this  resultant  should  be  larger  than  the  resultant  of  the  reaction  forces 
2p  sin  a  : 

2fp  .  cos  a>2p  sin  a,  or  f>tga,  tg(p>tga,  i.e.  a<q>. 

Hence  the  condition  allowing  the  product  to  be  drawn  into  the  working 
space  may  be  formulated  thus  : 

It  is  requisite  that  the  angle  of  grasping  a  should  be  less  than  the  angle  of 
friction  of  tJie  product  and  the  working  surface.  Considering  that,  given 
one  and  the  same  size  of  product,  the  angle  a  depends  on  the  radius  of 
the  rollers,  by  modifying  this  radius  we  are  always  able  to  select  a  <  (p. 

The  dependence  of  the  length  of  the  radius  on  the  size  of  the  product 
may  be  deduced  from  the  following  considerations.  Let  us  imagine  we 
have  two  rolls  of  a  radius  r,  the  distance  between  them  is  i?0  (Fig.  191),  the 
size  of  the  product  fed  in  r\.  After  the  product  has  passed  between  the 
rolls  it  is  reduced  to  the  size  j?0.  It  is  clear  that 

0  Ol=2r  cos  a-{-??=2r-f-*70 ; 
by  deducing  herefrom  the  r,  we  obtain  : 


Consequently,  knowing  the  primary  and  the  final  size  of  the  product, 
we  can  define  the  radius  of  the  rolls,  for  a  is  known  to  us — it  must  in  its 
limit  be  equal  to  9?.  Generally  speaking  the  angle  a  is  comparatively 
small,  and  therefore  with  a  more  or  less  admissible  approximation, 

may  accept  sin  ~=~.     Then 

L       L 


Hence  it  follows,  that  the  greater  the  angle  of  friction  the  less  is  the 
radius  of  the  rolls  for  grasping  the  product  of  a  given  size.  This  means 
that  the  diameter  of  the  porcelain  rolls  ought  to  be  less  than  the  diameter 
of  the  cast  iron  ones,  for  the  coefficient  of  friction  of  porcelain  and  the 
product  is  greater  than  that  of  cast  iron  and  the  same  product.  Such 
material  as  porcelain,  however,  cannot  always  be  successfully  employed 
for  making  rolls,  as  the  very  great  stresses  set  up  in  the  process  of 
reduction,  which  in  such  cases  can  have  a  detrimental  effect  upon  the 
porcelain,  must  be  taken  into  consideration, 


212  FLOUR    MILLING  [CHAP,  iv 

The  Materials  and  Design  of  Rolls. — The  materials  of  which  rolls  are 
prepared  must  be  hard  and  wear-resistant. 

If  the  product  is  to  be  reduced  by  cutting,  it  is  necessary  that  the 
coefficient  of  friction  should  be  the  least  possible,  as  the  force  of  friction  is 
obnoxious  here.  But  if  the  rolls  operate  on  the  principle  of  trituration 
(Fig.  136,  p.  154),  then  the  force  of  friction  renders  useful  service  ;  a 
high  coefficient  of  friction,  therefore,  is  desirable  in  that  case.  The  choice 
of  material,  however,  is  determined  by  its  durability,  wear-resistancy, 
and  mouldability.  General  practice  has  shown  that  cast  iron,  steel,  and 
porcelain  answer  those  requirements. 

The  iron  rolls  are  cast  so  that  their  surface  is  hardened  5  to  10  mm. 
deep  from  the  surface.  The  hardening  of  the  surface  of  the  rolls  is  brought 
about  by  casting  them  in  metal  fining-pots  or  by  other  means,  which  are 
the  secrets  of  the  factories. 

The  attempt  to  use  steel  was  unsuccessful ;  it  must  be  admitted,  though, 
that  this  question  has  been  but  little  treated  by  engineers.  It  is  probable, 
however,  that  rolls  of  ingot  iron  with  a  cemented  (hardened)  surface 
would  give  better  results  than  cast  iron,  and  the  engineering  firms  ought 
to  work  in  that  direction. 

Porcelain  rolls  were  first  introduced  by  Wegmann's  factory.  The 
durability  of  porcelain  rolls  is  not  as  great  as  that  of  cast  iron,  but  for 
semolina-grinding  they  are  indispensable.  At  first,  some  twenty  years 
ago,  the  porcelain  rolls  were  not  quite  satisfactory,  often  bursting  on 
becoming  heated,  and  they  became  rapidly  and  irregularly  worn.  Nowa- 
days, however,  the  exhausting  of  roller  mills  having  been  improved  and 
durable  porcelain  being  available,  they  compete  with  cast-iron  rolls 
quite  successfully. 

The  composition  of  the  roll-porcelain  is  approximately  : 

Pure  china  clay        .....     61-62  per  cent. 

Fine  quartz 16-17         „ 

Feldspar 16-17 

Chalk 4 

As  regards  the  designs  of  rolls,  those  of  cast  iron  are  generally  hollow 
cylinders  A  (Figs.  192  and  193)  which  are  set  on  the  shaft  B  hot,  and  are 
seldom  keyed  on.  This  construction  (Fig.  193)  is  more  convenient  if 
cast ;  when  at  work  the  roll  warms  more  evenly,  and  therefore  its  expan- 
sion evenly  modifies  tke  dimensions,  leaving  the  cylindric  shape  unaltered. 

The  porcelain  rolls  (Fig.  194)  consist  of  a  full  cylinder  A,  caught  be- 
tween cast-iron  washers  C  by  means  of  coupling  bolts  d.  In  the  washers 


CHAP.    IV] 


FLOUR   MILLING 


213 


there  are  holes  for  the  shaft  B.     A  general  view  of  a  grooved  roll  is  given 
in  Fig.  195. 

Position  of  the  Rolls. — The  position  of  the  rolls  in  the  frame  materially  in- 
fluences the  design  of  other  parts  of  the  machine,  the  degree  of  wear  of  the 
rolls  themselves,  and  the  compactness  of  the  whole  machine.  In  choosing  a 
position  for  the  rolls  the  constructor  must  be  guided  in  the  first  place  by 
considerations  of  a  convenient  supply  of  the  product  to  the  milling  surfaces, 


\Wmm^^M 

^    6OQ. 


FIG.  192. 


FIG.  193. 


and  easy  access  for  inspecting  the  operation.  Modern  practice  allows  eight 
different  combinations  of  the  rolls,  which  we  shall  examine  now  (Fig.  196). 
The  first  three  combinations — 1,  2,  and  3 — relate  to  double  roller 
mills.  Combination  1  with  the  axes  lying  in  a  horizontal  plane,  in  re- 
spect to  the  supply  of  the  product  and  inspection  of  the  work  offers 
an  undoubted  advantage  over  the  second,  which  was  suggested  with 
a  view  to  reducing  the  breadth  of  the  machine,  which  is  important 
for  mill-buildings  deficient  in  space.  But  a  material  defect  of  the  vertical 
position  of  the  rolls  is  the  more  complicated  feeding  of  them,  i.e.  the  supply- 


FIG.  194. 


FIG.  195. 


ing  of  the  product  to  the  working  surfaces.  Combination  3  gives  a  diagonal 
disposition  of  the  rolls,  owing  to  which  the  complex  construction  of  the 
feeding  device  is  discarded,  and  at  the  same  time  the  machine  gains  in 
compactness  in  comparison  to  combination  1.  Combinations  4  and  5  are 
designed  to  afford  the  product  two  passages  between  three  rollerk  These 
combinations,  however,  should  be  most  decidedly  rejected,  as  the  middle 
rolls  are  placed  in  working  conditions  different  from  those  on  either 
side.  In  doing  double  work,  they  wear  out  considerably  faster  than  the 
outer  rolls,  owing  to  which  the  operation  of  the  mill  becomes  irregular 
and  inferior  in  quality.  In  addition,  the  feeding  of  the  rolls  requires 


214 


FLOUR   MILLING 


[CHAP,  iv 


a  complicated  apparatus  and  the  inspection  of  the  work  is  difficult. 
Combination  8  offers  a  double  passage  of  the  product.  The  designs  of 
machines  of  that  combination,  purporting  to  give  two  passages,  one 
succeeding  the  other,  are  senseless,  if  only  from  the  fact  that  they 
infringe  the  principle  of  a  single  treatment  of  the  product.  Machines 
of  this  type  are  offered  for  use  in  plain  farm  milling,  which  is  quite 
successfully  performed  by  stone  mills. 

The  machines  where  the  product  after  the  first  passage  is  delivered 
to  be  bolted,  and  the  large  product  sifted  off  is  then  fed  to  the  lower  pair 


FIG.  196. 

of  rolls  for  further  treatment,  are  complicated  in  construction  and  are 
now  almost  entirely  discarded. 

There  remain  but  two  combinations — 6  and  7.  The  fact  is  that  the 
four-roller  machines  are  the  usual  modern  type  of  the  roller  mill.  Not 
only  in  industrial  mills,  but  in  small  country  mills  also,  two-roller 
mills  are  a  rarity.  This  is  easily  understood  since  one  four-roller  mill 
is  considerably  cheaper  than  two  mills  with  two  rolls  each. 

Combination  6  is  accepted  by  all  American  factories,  and  but  at  one, 
Hantz  in  Austria-Hungary,  in  Europe.  Combination  7,  with  a  diagonal 
disposition  of  the  rolls,  has  been  accepted  by  all  European  makers. 

When  studying  the  designs  of  mills  with  a  horizontal  and  diagonal 


CHAP,  iv]  FLOUR   MILLING  216 

disposition  of  the  rolls,  we  shall  estimate  the  merits  and  point  out  the 
defects  of  those  combinations. 

The  Character  of  the  Surface  and  the  Motion  of  the  Rolls. — The  process 
of  reducing  grain  to  flour  in  the  form  it  exists  in  modern  flour  milling 
technics  is  divided  into  two  parts.  At  first  the  grain  is  crushed  into 
small  particles  (middlings  and  dunsts — very  fine  middlings),  and  then 
after  the  middlings  and  dunsts  have  been  graded  according  to  size 
(sifted)  and  quality,  they  are  reduced  to  flour.  The  first  operation  is 
named  breaking  and  the  second  is  the  reduction  proper.  At  a  compara- 
tively recent  date,  there  has  been  introduced  into  Russian  milling  plants 
another  operation  or  second  breaking  of  the  cleaned  middlings  (called 
"  Auflosung  "  in  Germany)  or  the  polishing  of  middlings,  as  we  name 
it.  The  aim  of  breaking  is,  by  only  slightly  crushing  the  integument, 
and  obtaining  as  little  flour  as  possible,  to  reduce  the  grain  to  middlings 
coarse  and  fine,  from  which  it  is  easy  to  extract  the  particles  containing 
bran  and  imparting  a  dark  colouring  to  the  flour. 

These  two  fundamental  operations  determine  the  character  of  the 
working  surfaces  of  the  rolls.  For  breaking  the  rolls  are  covered  with 
grooves,  having  an  effect  similar  to  the  chipping  (p.  154,  Fig.  135)  or 
cutting.  The  chisels  on  the  surface  of  the  roll  are  named l  corrugations  or 
grooves,  and  the  rolls  are  said  to  be  corrugated.  In  accordance  with  the 
size  of  the  product,  which  is  broken  up  into  smaller  particles  by  the 
corrugations,  the  size  of  the  grooves,  fluting  or  corrugations  varies.  The 
shape,  size,  and  dispositions  of  the  corrugations  will  be  spoken  of  in  a 
special  chapter  ;  at  present  the  fact  must  be  mentioned  that  the  stock  is 
passed  through  the  corrugated  rolls  from  two  to  nine  times,  depending  on 
the  kind  of  milling.  Consequently  the  size  of  the  corrugations  as  well  as 
other  elements,  which  define  them,  likewise  are  varied.  But  the  general 
character  of  the  break  rolls  remains  the  same,  i.e.  the  surface  is  covered 
with  grooves  of  a  greater  or  smaller  size.  As  there  are  coarse  middlings 
yielded  during  the  process  of  breaking,  the  treatment  of  which  cannot 
be  performed  on  break  rolls,  they  are  separated  and  conveyed  to  special 
machines,  also  with  corrugated  rolls,  for  further  reduction.  Such  rolls 
are  called  rebreaks  in  Russia  and  are  used  almost  exclusively  in  Russian 
mills  (the  Germans  call  them  "  Koppenstiihle  ").  Thus  both  first  and 
second  break  rolls  have  a  corrugated  surface. 

For  the  reduction  of  cleaned  coarse  and  fine  middlings  the  surface 
of   the   rolls    is    smooth.      Here   the   reduction   is   performed    on   the 


1  Corrugations,  grooves,  flutes  are  all  quite  synonymous  terms.     "  Grooves  "  are  perhaps 
more  commonly  spoken  of  in  England  than  either  of  the  other  terms. 


216  FLOUR    MILLING  [CHAP.  IV 

principle  of  trituration  (p.  154,  Fig.  136).  When  studying  the  principles 
of  reduction,  we  saw  that  the  work  of  trituration  is  performed  by  the 
force  of  friction  Nf,  where  N  is  the  pressure  of  the  working  organ  upon 
the  product,  and  /  the  coefficient  of  friction  of  the  product  against  the 
working  surface.  The  greater  /  is,  the  less  is  the  pressure  of  the  rolls 
upon  the  stock,  and  the  less  will  the  wear  of  the  working  surface  and  of 
other  parts  of  the  machine  be.  Besides  that,  if  the  pressure  of  the 
rolls  upon  the  product  be  heavy,  the  quality  of  the  flour  deteriorates ; 
the  flour  is  "  dead,"  i.e.  has  a  low  baking  quality,  as  proved  by 
experiments.  Great  pressure  produces  bad  results  in  the  milling  of 
flour  of  high  quality,  while  the  lower  kinds  are  less  influenced  by  it.  For 
this  reason  the  surface  of  the  grinding  rolls  should  have  the  largest 
possible  coefficient  of  friction  /.  In  this  respect  porcelain  rolls  or  the 
dull  surface  of  cast-iron  rolls  produce  satisfactory  results,  though  the 
dull  surface  of  the  cast  iron  becomes  polished  rapidly  and  requires 
frequent  renovation. 

To  procure  flour  out  of  the  branny  particles  (dark  middlings),  a 
heavy  pressure  has  to  be  applied,  which  the  porcelain  cannot  support. 
The  dull  surface  of  the  cast-iron  rolls  is  so  rapidly  worn,  that  there  is 
no  sense  in  using  it.  Therefore  a  polished  cast-iron  surface  has  to  be 
used  and  a  strong  pressure  given  to  the  rolls,  so  as  to  obtain  a  sufficiently 
great  force  of  friction  Nf. 

Thus  we  have  three  kinds  of  roller-surfaces  :  (1)  corrugated  for 
breaking,  (2)  rough  surfaces  with  a  large  coefficient  of  friction  (porcelain, 
dull  cast  iron)  for  reducing  the  middlings,  and  (3)  the  smooth-polished 
cast-iron  surface  for  milling  the  lower  kinds  of  flour. 

Let  us  now  turn  to  the  character  of  motion  of  the  rolls. 
When  studying  the  movement  of  the  product  in  the  working  space  of 
the  rolls,  we  noticed  that  the  rolls  rotate  in  opposite  directions,  pushing 
the  grain,  or  particles  of  it,  in  the  direction  of  the  line  of  grinding.  The 
greater  the  revolving  speeds  of  the  rolls,  the  higher  is  their  capacity. 
But  this  velocity  has  a  limiting  signification,  which  is  determined  by 
the  degree  of  heating  of  the  product,  which  must  not  exceed  30°  to  40°, 
otherwise  the  flour  may  likewise  become  deadened.  The  limiting  significa- 
tion of  the  circumferential  velocities  of  the  rolls  will  be  given  later,  while 
it  must  be  pointed  out  now  that  their  magnitudes  are  different  for  each  roll. 
This  is  indispensable  to  obtain  a  cutting  effect  on  the  corrugated 
rolls  and  trituration  on  smooth  rolls.  If  the  velocities  of  both  the  rolls 
were  equal,  the  stock  would  be  chipped  radially  on  the  corrugated  rolls, 
and  would  blind  the  space  between  the  corrugations  by  a  radial  pressure. 


CHAP,   iv] 


FLOUR   MILLING 


217 


A  continued  operation  of  the  rolls  would  lead  to  a  crushing  of  the  product 
to  cake,  if  the  grain  were  sufficiently  soft,  or  to  flour,  if  it  were  very  hard. 
Consequently,  there  could  be  no  idea  of  breaking  in  the  sense  we  under- 
stand it.  The  same  kind  of  crushing  the  product  to  cakes  would  take 
place  on  the  smooth  rolls  too. 

Our  aim,  however,  in  the  breaking  process  is  to  obtain  a  uniform 
product  approximately  corresponding  to  half  the  size  of  the  least 
distance  between  the  working  surfaces.  For  this  reason  different  velo- 
cities are  imparted  to  the  rolls.1  Then  the  slowly  rotating  roll  carries 
the  product  to  the  one  revolving  rapidly,  which  cuts  off  part  of  the  product 
with  the  chisel  of  the  corrugation  in  the  breaking  process  and  chips  it  off 
by  the  force  of  friction  in  grinding.  'Only  under  such  conditions  does 
the  direction  of  the  active  force  coincide  with  the  route  of  the  product,  and 
part  of  it,  the  size  of  which  is  determined  by  the  distance  between  the 
working  surfaces,  is  separated  off.  It  is  important  to  note  that  even  if  it 
were  possible  to  avoid  crushing  the  product  to  cakes  by  rolls  rotating  with 
equal  velocities,  the  pressing  forces,  acting  perpendicularly  to  the  direction 
in  which  the  product  travels,  would  crush  it  to  particles  of  various  sizes, 
depending  but  little  on  the  least  distance  between  the  working  surfaces. 

The  circumferential  velocity  of  the  rolls  is  determined  according  to  their 
diameter  and  number  of  revolutions,  the  relation  of  velocity  of  the  slowly 
and  the  rapidly  revolving  rolls  varying  between  1-1:1  and  5:1.  The 
following  table  gives  a  clear  idea  of  the  limits  of  the  sizes  of  the  diameters, 
number  of  revolutions,  and  velocities  of  the  rolls.  In  this  table  D  denotes 
the  greatest  and  the  least  diameters  of  the  rolls,  N  the  number  of  revolu- 
tions of  the  fast  roll,  V  their  circumferential  velocities  in  metres  per  second, 
V :  F!  the  differential  velocities  of  the  fast  and  slow  rolls. 


TABLE  XXI 


Rolls. 

D  mm. 

N, 

Fmt.  per  sec. 

V:V1 

6-9  breaks 

150-350 

225-480 

3-0-4-7 

2-5  :  1-5  :  1 

2-5  breaks 

220-380 

250-600 

3-0-6-0 

2  :  1-3  ."1 

1-3  rebreaks    .       ••„'.•'•„• 

220-350 

250-400 

2-5-3-5 

1-2    1-1-6:1 

Grinding  cast  iron    .         . 

150-400 

180-380 

3-0-3-6 

1-1    1-1-3:1 

Grinding  porcelain   . 

220-350 

150-180 

2-0-2-75 

1-1    1-1-5:1 

The  factories  in  Europe,  England  excepted,  generally  give  the  averages 
of  those  quantities,  namely,  D  of  the  corrugated  rolls  220-300  mm., 

1  This  is  known  as  the  "  Differential." 


FLOUR   MILLING  [CHAP,  iv 

smooth  250-350  mm.,  ^=200-320.  Some  of  the  English  factories 
(Thos.  Robinson)  give  D  =  150-400  mm.,  and  N  up  to  480.  So  great  a 
diameter  as  400  mm.  is  used,  but  in  one  make  of  Robinson's  mills  the 
different  velocities  of  a  pair  of  rolls  are  obtained  through  their  different 
diameters.  This  construction  is  described  below. 

The  American  factories  (Allis-Chalmers  Co.)  usually  give  D= 175-250 
mm.,  but  with  a  much  higher  number  of  revolutions,  up  to  600  for  the 
rapidly  rotating  rolls  with  a  diameter  of  175  mm.,  which  corresponds 
to  the  circumferential  velocity  of  5*35  metres  per  second.  The  mills  of 
Nordyke  &  Marmon  Co.,  designed  for  the  preparation  of  various  cereal 
flakes  of  barley,  oats,  maize,  &c.  (the  celebrated  American  "  Hercules  " 
oat  flakes,  known  in  Russia  but  in  the  form  of  unsuccessful  adulterations), 
have  rolls  up  to  460  mm.  in  diameter,  and  the  greatest  number  of  revolu- 
tions of  the  fast  roll  is  120,  which  corresponds  to  a  circumferential 
velocity  of  2*9  metres  per  second. 

Having  become  acquainted  with  the  general  character  of  the  working 
organs  of  roller  mills  we  shall  proceed  to  study  in  detail  the  corrugating 
of  break  and  scratch  rolls. 


2.  Corrugating  the  Rolls 

General  State  of  the  Question. — The  question  concerning  the  most 
advantageous  operation  of  the  breaking  mills  may  not  be  regarded  as 
solved  until  the  question  touching  the  correct  corrugating  of  rolls  is  settled. 

Until  now,  the  specialist,  when  a  problem  of  corrugating  the  rolls  of 
break  mills  was  set  before  him,  solved  it  by  simply  pointing  out  the  number 
of  corrugations,  and  never  touched  the  other  essential  sides  of  corrugating. 
It  is  not  surprising,  therefore,  that  not  only  flour-millers,  but  by  far  the 
greater  number  of  specialists  too,  would  express  astonishment  if  ques- 
tioned as  to  the  incline  of  the  corrugations.  It  is  a  totally  unknown  fact 
to  them  that  the  incline  of  the  corrugations  in  respect  to  the  generating 
circle  of  the  rolls  varies  from  the  first  to  the  last  break,  and  that  the 
degree  of  perfection  of  the  break  process  depends  on  it. 

How  is  the  cutting  of  rolls  done  in  mills  provided  with  corrugating 
machines,  or  at  factories  undertaking  such  work  ?  Almost  always  with 
the  same  inclination  of  the  corrugations.  And  yet  this  is  a  grave  error. 

But  besides  the  inclination  of  the  corrugations,  there  is  another  side 
to  the  cutting,  to  which  no  serious  attention  has  been  paid  by  the  Euro- 
pean, not  to  mention  the  Russian,  experts.  It  is  the  disposition  of  the 
angles  of  the  corrugations,  of  their  cutting  edges  in  respect  to  the  product 


CHAP,  iv]  FLOUR    MILLING  219 

treated  at  the  different  moments  of  breaking.  Almost  at  all  the  mills  in 
Russia  without  exception  the  corrugations  on  the  breaking  rolls  are  set 
so  that  the  product  is  subject  to  the  effect  of  the  sharp  cutting  angles  of 
the  corrugations.  This  is  looked  upon  in  a  totally  different  light  by  the 
Americans,  who,  beginning  with  the  fifth  break  in  high  milling,  discon- 
tinue the  carrying  of  the  product  by  the  sharp  angles  of  the 
corrugations  on  the  slow  roll  to  the  likewise  sharp  cutting  angles  of  the 
fast  roll. 

Besides  the  number  of  corrugations,  their  inclination,  and  the  position 
of  the  cutting  angles  in  respect  to  the  product  under  treatment,  the  shape 
of  the  corrugation  is  likewise  an  important  item. 

Thus,  before  giving  an  exhaustive  answer  to  'the  question,  how 
the  corrugations  of  the  rolls  should  be  cut,  this  question  has  to  be 
decided. 

In  investigating  the  question  concerning  the  corrugating  of  the  rolls, 
the  following  items  must  be  settled  upon  : 

(1)  Shape  of  the  corrugations. 

(2)  Their  incline. 

(3)  Disposition  of  the  cutting  angles  of  the  corrugations  in  respect  to 
the  product. 

(4)  Number  of  corrugations. 

It  were  an  error  to  think  that  any  of  these  four  demands  are  of  a 
greater  or  less  importance.  The  number  of  corrugations,  their  position, 
incline,  and  form  are  all  equally  important  in  the  breaking  process.  Even 
if  our  mills  are  able  to  supply  us  with  a  satisfactory  kind  of  flour,  while 
giving  attention  but  to  the  number  and  shape  of  the  corrugations  (the 
latter  is  not  always  the  case),  there  is  yet  no  doubt  the  milling  would  rise 
in  quality,  if  a  correct  inclination  and  positioning  of  the  cutting  angles 
were  imparted  to  the  corrugations. 

Shape  of  the  Corrugations. — When  examining  the  question  of  the 
shape  of  the  corrugations  it  must  be  noted  that  the  theory  and  practice 
existing  afford  too  little  material.  In  such  important  works  as  the  books 
of  Professor  K.  A.  Zworykin  and  Professor  F.  Kick,  we  find  but  the  most 
general  remarks.  In  the  more  recent  works  of  Baumgartner  and  Ketten- 
bach  there  are  more  data  touching  that  question.  But  both  of  these 
German  authors  do  not  look  deeply  enough  into  it,  alluding  only  to  the 
results  obtained  in  factory  practice,  and  giving  no  time  to  a  necessary 
critical  estimation  of  the  corrugating  of  rolls  in  vogue. 

The  milling  engineers,  regarding  the  breaking  process  as  a  cutting 
of  grain  or  particles  of  it,  produce  corrugations  of  one  shape  mostly,  with 


FLOUR   MILLING  [CHAP,  iv 

sharp  angles,  characterising  it  only  by  the  size  of  the  angle  of  the  corruga- 
tion itself.  Fig.  197  shows  us  the  angle  of  50°,  established  by  practice 
for  corrugations  in  high  milling  of  wheat,  and  Fig.  198  reproduces  the 
shape  of  the  corrugation  with  an  angle  of  75°  employed  in  the  simplified 
wheat  and  high  rye  milling. 

The  drawings  of  Figs.  197  and  198  prove  that  those  angles  of  corruga. 
tions  are  easily  obtained.  The  front  facet  of  the  corrugation  (Fig.  197) 
forms  a  diametrical  plane  of  the  rolls  for  an  angle  of  50°,  and  a  segmental 
plane  (Fig.  198)  for  an  angle  of  70°-75°,  the  r  in  the  second  case  being 
equal  to  f- — ^  E. 

It  is  not  difficult  to  show  (Fig.  197)  that  given  such  angles  and  a 


\ 

\ 

\ 
\ 


FIG.  197. 

certain  number  of  corrugations,  their  height  is  a  quite  definite  quantity. 
Indeed,  if  we  denote  through  n  the  number  of  corrugations  to  a  centi- 

metre of   circumference  of  the  roll,  t  their  height,  and  h  =  -  '  the 

circular  pitch  of  the  corrugations,1  then  from  the  triangle  ABC  we  shall 
obtain  for  t  in  millimetres  : 


p)       .......     .      (1), 

supposing,  with  a  slight  error,  that  the  tangent  passing  through  the 
point  A  of  the  corrugation  passes  at  the  same  time  through  its  point  B. 
Hence  it  is  clear  that  with  an  increased  number  of  corrugations  to  a 
centimetre  their  t  decreases.  If  we  take  the  number  of  corrugations  n 

1  The  circular  pitch  of  the  corrugations  is  the  part  of  the  area  between  two  points  of  the 
corrugations,  but  for  the  simplicity  of  the  inference  h  may  denote  a  chord  of  this  arc  or  a  tangent, 
as  the  mistake  occurring  from  this  inference  is  insignificant. 


CHAP,  iv]  FLOUR    MILLING  221 

equal  to  5  and  10,  and  /?=50°,  then,  according  to  formula  (1)  we  obtain 
corresponding  t's  in  millimetres  : 

*==i^gr400  =  l-68  mm.,  and  J=~ty400=0'84  mm. 
o  1U 

The  shape  of  the  corrugations,  having  an  angle  of  50°,  defined  by  the 
construction  derived  from  Fig.  197,  is  generally  used  in  high  grinding. 
For  the  medium,  low,  and  rye  grinding  general  practice  has  established 
the  shape  of  corrugations  given  in  the  design  on  Fig.  198,  the  radius  r 
accepted  for  the  medium  grinding  being  less  than  the  one  used  in  low 
and  rye  grinding. 

Let  us  see  how  the  height  of  the  corrugation  will  be  defined  in  this 
case,  the  number  of  corrugations  to  a  centimetre  being  given. 

Having  denoted  the  angle  of  the  corrugation  ft,  the  angle  formed  by 


FIG.  198. 

the  radius  R  passing  through  the  point  of  the  corrugation  and  its  lower 
facet  7,  the  circular  pitch  of  the  corrugation  h,  and  its  height  through  t, 
we  can  define  the  height  t  of  the  corrugation. 

The  angle  y,  usually  equal  to  75°,  and  the  radius  of  the  roll  R  and  r 
being  given,  previously  to  defining  t  the  angle  y  and  the  circular  pitch  of 
the  corrugation  h  have  to  be  defined  in  accordance  with  the  quantities  given. 

The  angle  y  is  deduced  from  AAOC  by  sin  y, 

r=R  sin  y,  hence  sin  y  =-5. 

K 

The  circular  pitch  of  the  corrugation  h  may  be  easily  defined,  with  a 
slight  error,  either  as  an  arc  AB,  taken  as  a  straight  line,  or  as  its  chord. 
In  the  latter  case  the  circular  pitch  h  is  defined  as  the  side  of  an  oblique- 
angled  triangle  ABD. 

We  shall  take  the  second  case,  it  being  more  simple  and  giving  an 


222  FLOUR    MILLING  [CHAP,  iv 

insignificant  error.  Granted  that  the  tangent  AS  passes  through  the  top 
of  the  second  corrugation  B,  i.e.  coincides  with  the  chord,  and  forms  like- 
wise with  the  radius  OB  a  right  angle.  Then  we  obtain  L  BAD  =  90  —  a, 
LABD  =  90  -  y,  and,  consequently,  L  ABD  =  180  -(90  -  a)  -(90  -  y) 


The  triangle  ABD  gives  : 

AB  BD 


. 
sin  (180-0)     sin  (90  -a)' 

If  t  is  the  height  of  the  triangle  ABD  dropped  on  to  AB,  i.e.  the 
height  sought  for  of  the  corrugation,  we  obtain  t=BD  sin  (90—  y). 
Hence,  by  substituting  the  signification  in  the  place  of  BD  and  per- 
forming the  simplifications  (a=0—  y),  we  obtain  the  t  sought  for  : 

cosj^-vjw 
sin  p 

In  this  formula  all  the  quantities  are  known,  for  h  is  defined  in  accord- 
ance with  the  number  of  corrugations  per  centimetre,  the  angle  /?  is  given, 
and  the  angle  y  is  defined,  as  explained  above. 

If  we  take  the  diameter  of  the  roll  to  be  250  mm.,  i.e.  .8  =  125  mm., 
r=40  mm.,  0=75°,  and,  having  defined  y  out  of  the  formula 

sin  y=-^=—  —  (y  =  18°40/),  substitute  them  into  the  formula  (2)  then,  the 

number  of  corrugations  being  5  and  10  to  1  centimetre,  we  obtain  after 
a  calculation  : 


Having  reckoned  out  and  compared  the  signification  t  of  the  corruga- 
tions for  high  milling,  with  the  same  number  of  them  10  per  1  cm., 
and  an  angle  of  75°,  we  obtain  Z=0'76  mm.  This  shows  that  the  height 
of  the  corrugations  in  the  second  case  is  considerably  less  —  0'54  mm., 
i.e.  by  0*22  mm. 

Besides  the  corrugations  of  a  triangular  shape  just  examined,  the  use 
of  corrugations  with  rounded  cutting  edges  has  been  suggested.  But  this 
form  is  justified  neither  by  theory  nor  by  practice,  whence  the  theoretical 
premises  are  deduced.  The  third  shape  of  corrugations,  trapezoidal  in 
section,  as  shown  on  Figs.  199  and  200,  is  still  recommended  by  some 
factories  and  specialists,1  who  maintain  that  the  cutting  of  the  grain,  or 

*  FT.  Kettei*bach,  Der  Muller  und  Muhlenbauer,  1907? 


CHAP.    IV] 


FLOUR   MILLING 


223 


particles  of  it,  is  more  perfect  in  that  case,  for  the  integument  of  the 
grain  remains  whole.  There  is  no  logical  justification  for  this,  however, 
for  in  the  breaking  process  the  cutting  up  of  the  bran  is  unavoidable. 
Further,  the  cutting  of  such  corrugations  is  undoubtedly  in  worse  con- 
dition even  by  the  type  itself  of  the  cutting  operation,  not  to  mention 
the  fact  that  the  friction  of  the  flat  part  of  the  corrugations  against 
the  product  generates  superfluous  work. 

The  French  factory,  Teisset,  Chapron  &  Brault  Fr.,  very  seriously 
recommends  corrugations,  shown  on  Fig.  201  with  a  large  circular  pitch 
for  the  main  corrugation,  and  small  intermediate  corrugations,  main- 


Ist  break 


FIG.  199. 


4th  break 


FIG.  201. 


FIG.  200. 


taining  that  such  an  arrangement  increases  the  yield  of  semolina,  and 
consequently  the  number  of  breaks  may  be  reduced.  The  utility  of 
this  arrangement,  however,  is  doubtful,  for  the  inner  corrugations  will 
not  work.  In  addition,  the  corrugating  of  the  rolls  has  to  be  performed 
either  with  a  forming  tool  or  in  two  turns,  which  presents  great  difficulties. 

For  feed  milling,  G.  Barat  (France)  has  lately  suggested  the  use  of 
pyramidal  corrugations  obtained  by  cross-corrugating  at  a  right  (Fig.  202) 
and  a  sharp  (Fig.  203)  angle,  but  up  to  the  present  corrugations  of  this 
shape  have  been  used  in  America  only  for  stone-crushing  and  compressing 
refuse  in  the  production  of  oil  from  cotton  seeds. 

This  is  all  that  has  been  evolved  by  practice  and  theory  regarding  the 
shape  of  corrugations. 


224 


FLOUR   MILLING 


[CHAP,  iv 


Let  us  see  now  what  requirements  the  shape  of  corrugations  should 
answer,  from  the  point  of  view  of  the  least  expenditure  of  energy  in  the 
breaking  process. 

The  aim  of  the  breaks  is  to  obtain  as  many  middlings  as  possible 
with  the  least  possible  breaking  of  the  bran  coverings.  The  ideal 
position  of  the  grain  in  first  break  rolls  is  shown  in  Fig.  204.  In  this 


FIG.  202. 


FIG.  203. 


case  the  grain  would  be  broken  through  its  crease.     The  transversal 
position  given  on  Fig.  205  is  less  favourable  for  the  first  breaking. 

From  the  point  of  view  of  the  theory  of  cutting,  the  shapes  of  corru- 
gations examined  exclude  all  possibility  of  cutting.  Indeed,  the  shape 
of  corrugations,  defined  by  Fig.  197,  gives  a  cutting  angle  of  90°,  for 
this  angle  is  defined  by  the  front  edge  of  the  chisel  (Fig.  204)  and  the 
direction  of  its  motion,  which  may,  with  an  insignificant  error,  be  re- 


FIG.  204. 


FIG.  205. 


FIG.  206. 


garded  as  straight.  The  cutting  force  l  P=P2tga,  for  P2,  the  force  of 
pressure,  is  perpendicular  to  the  front  edge  of  the  chisel  A  ;  P3,  the 
chipping  force,  is  perpendicular  to  the  direction  in  which  the  chisel 
moves,  and  a  is  the  cutting  angle.  If  a  =  90°,  then  P=  oo.  That  is  to 
say,  the  grain  is  not  cut,  but  broken.  Should  the  shape  of  the  corruga- 
tion be  as  defined  by  Fig.  198,  a>90°.  Then  P  is  a  negative  quantity, 
which  means  that  the  breaking  of  grain  is  performed  under  worse  con- 
ditions than  in  the  first  case  (Fig.  206).  In  the  so-called  "  Hochschrot," 

1  £>ee  Prof,  I.  Time's  theory  of  cutting. 


FLOUR    MILLING 


225 


CHAP.    IV] 

when  the  slowly-rotating  roll  is  smooth  (Fig.  207)  or  has  fine  corrugations 
(Fig.  208),  it  is  quite  plain  that  the  grain  is  broken  and  that  part  of 
the  bran,  coming  in  contact  with  the  smooth  or  finely-cut  surface  of 
the  slowly  revolving  roll,  is  ground.  That  is  the  reason  why  "  Hoch- 
schrot "  produces  the  so-called  "  blue  flour,"  which  is  generally  extracted 
on  the  brush  machine. 

Now,  if  we  set  before  ourselves  the  problem  of  obtaining  a  perfect  cutting 
of  grain  or  particles  of  it  in  the  breaking  process  and  leaving  the  integu- 
ment whole,  with  the  view  of  obtaining  a  greater  amount  of  broad  bran, 
then  the  fast  roll  has  to  be  supplied  with  corrugations  having  cutting 
angles  of  45°,  as  shown  on  Fig.  209,  which  proves  that  the  feeding  roll 
may  have  ordinary  corrugations.  The  cutting  of  corrugations  of  that 
shape  on  cast  iron,  however,  would  present  some  difficulty  by  reason  of 
its  brittleness.  Therefore,  taking  into  consideration  the  incline  of  the 


FIG.  207. 


FIG.  208. 


corrugation  in  regard  to  the  generating  circle  of  the  roll,  this  angle  may 
be  accepted  as  exceeding  45°,  namely  60-65°,  which  has  a  small  cutting 
effect. 

A  solution  of  this  question  is  likewise  possible  if  the  rolls  are  made  of 
ingot  iron,  and  not  of  cast  iron  with  a  hardened  surface.  It  is  quite 
possible  to  use  ingot  iron  (open-hearth  steel).  The  rolls  may  be  consider- 
ably lighter,  and  a  cementation  of  the  corrugations  which  would  guarantee 
their  wear  to  be  less  than  that  of  the  corrugations  on  cast-iron  rolls  is 
attainable,  as  proved  by  Professor  Zworykin's  experiments.1 

The  question  of  the  preparation  of  rolls  of  ingot  steel  is  very  important. 
Serious  attention  ought  to  be  paid  to  it  by  engineers,  because  a  satis- 
factory solution  of  that  question  would  cause  a  revolution  in  respect  to 
the  shape  of  the  corrugations,  resulting  in  a  more  perfect  breaking  pro- 
cess, owing  to  the  sharper  angle  of  the  corrugations. 

Incline  of  the  Corrugations. — Two  directions  for  the  cutting  edges  of 
the  corrugations  were  suggested  at  the  beginning  of  the  development  of 

1  See  "Cementation  of  Iron  by  Gas,"  by  Prof.  Zworykin,  Russian  Miller,  1911,  No.  2. 


226 


FLOUR   MILLING 


[CHAP,  iv 


roller-milling  ;  down  the  circumference  of  the  roll  and  along  its  generat- 
ing circle.  But  this  produced  unsatisfactory  results.  For  this  reason 
general  practice  in  the  end  adopted  the  direction  of  the  corrugations  at 
an  angle  to  the  generating  circle  of  the  roll. 

In  their  attempt  to  give  a  theoretical  explanation  of  the  results  ob- 
tained in  practice,  some  of  the  German  authors  (Fr.  Kettenbach  and  F. 
Baumgartner)  regard  the  breaking  down  of  grain  or  particles  of  it  as  a 
process  of  shearing.  Fig.  210  represents  the  edges  of  two  corrugations  : 
N  of  a  slowly  rotating  roll  and  N±  of  a  rapidly  revolving  one.  The  cutting 
of  the  grain  takes  place  when  the  corrugations  cross  at  the  point  0.  For 
the  sake  of  clearness  we  shall  carry  this  point  out  to  Ox.  When  the  edge 
of  the  corrugation  JV^  presses  upon  the  berry,  the  direction  of  the  cutting 


ZSn*. 


force  P  is  perpendicular  to  the  direction  of  the  corrugation.  If  the 
inclinations  a  (the  angle  a  in  respect  to  the  generating  circle)  of  the  corru- 
gations of  both  rolls  are  equal  in  size,  but  opposite  in  their  directions,  the 
angle  between  them  is  2  a.  Let  us  divide  the  active  power  P  according  to 
the  law  of  parallelograms  into  Z  horizontal  and  8  vertical.  The  cutting 
forces  will  be  S  —  8.  The  force  Z  tends  to  push  the  product  in  a  horizontal 
direction,  and  if  this  force  exceeds  the  force  of  friction  of  the  product 
against  the  surface  of  the  corrugation,  it  will  drive  the  product  to  the  end 
of  the  rolls,  having  annulled  the  cutting  force  8.  The  forces  P  and  Z 
depending  on  L  a  will  be  formulated  thus  : 

8—P  cos  a  ;    Z=P  sin  a. 

It  is  evident  that  the  power  Z  must  not  exceed  Pf,  i.e.  the  force  of 
friction  of  the  product  on  the  cast  iron,  where  P  is  the  normal  pressure 
and  /  the  coefficient  of  this  friction.  The  highest  and  the  limit  significa- 


CHAP,  iv]  FLOUR    MILLING  227 

tion  of  Z  is  when  it  equals  Pf.     Hence  it  is  clear  that  L  a  depends  on  /, 
which  may  be  defined  by  experiment.1 

The  coefficient  of  friction  f=tgq>,  q>  being  =  16-1 8°  for  cast  iron, 
and  up  to  22°  for  porcelain.  But  if  Z=Pf—P  sin  a,  the  result  is  : 

Sin  a=f=tg<p, 

i.e.  L  a  is  denned  as  an  angle,  the  sine  of  which  is  equal  to  the  tangent  of 
the  angle  of  friction. 

Coming  to  a  critical  estimation  of  F.  Baumgartner's  theory,  we  must 
say,  that  the  comparison  of  the  action  of  corrugations  to  that  of  shears  is 
not  accurate  enough. 

In  the  cutting  with  ordinary  shears  the  L  a  is  variable,  its  limit  being 
zero,  whereas  in  the  operation  of  the  rolls  L  a  is  a  constant  quantity. 
Consequently,  in  the  present  case  the  cutting  action  is  performed  by  non- 
parallel  edges,  in  opposition  to  the  normal  case,  when  the  edges  of  the 
cutting  instrument  are  parallel  to  each  other.  In  regard  to  the  expendi- 
ture of  cutting  force,  the  cutting  with  slanting  corrugations  is  disadvan- 
tageous, as  it  leads  to  the  loss  of  force  spent  in  pushing  out  the  product 
(force  Z). 

How  is,  then,  the  fact  to  be  explained  that  general  practice  has  evolved 
the  slanting  corrugations  ? 

If  the  sides  of  the  cutting  corrugations  were  parallel  to  the  generating 
circle,  the  cutting  would  be  effected  periodically.  But  if  an  inclination 
be  imparted  to  the  corrugations,  i.e.  the  cutting  edges  are  cut  on  the  curved 
surface  of  the  roll-cylinder,  then  the  product  is  .subjected  to  an  uninter- 
rupted cutting  action.  In  the  second  case  a  steady  cutting  force  is 
attained,  and  consequently  a  steady  load,  which  is  very  important  in 
the  work  of  every  machine. 

The  idea  may  be  elucidated  by  drawing  an  analogy  between  a  rapidly 
rotating  roll  and  a  milling  cutter  for  metal  or  wood,  where  the  cutting 
edges  are  directed  along  a  curve  of  the  cylinder.  Still,  we  must  say  that 
this  is  of  no  importance  in  the  operation  of  planing  machines,  for  they 
run  with  great  rapidity  (2500-6000  revolutions  per  minute),  owing  to 
which  the  intervals  parallel  to  the  generating  circle  are  quite  insignificant 
(0 '006-0 '002  of  a  second),  and  when  four  knives  are  in  operation,  scarcely 
influence  at  all  the  steadiness  of  the  load. 

The  small  number  of  revolutions  of  the  rolls,  which  is  accepted  now, 
makes  an  inclination  of  the  corrugations  indispensable.  But  this 
generates  the  Z  forces,  which  tend  to  a  one-sided  pressure  of  the  axis  upon 

i  Prof.  Kick,  Hehlfdbrileation,  1894. 


228  FLOUR    MILLING  [CHAP,  iv 

the  bearing,  which,  in  its  turn,  results  in  the  wear  of  only  one  collar  of 
the  bush  of  the  bearing,  the  right  or  left  hand  one— this  depends  on  the 
direction  in  which  the  /  corrugations  are  inclined— and  the  wear  of  one 
shoulder  of  the  axis  of  the  roll.  It  is  obvious  that  there  will  be  no  pres- 
sure upon  the  axis  only  in  case  a=0  (Z=P  sin  a=0),  i.e.  if  the  corrruga- 
tions  are  cut  in  a  generating  circle. 

Tending  to  discard  the  inclination  of  the  corrugations,  which  causes 
the  injurious  pressure  upon  the  axis,  we  must  increase  the  number  of 
revolutions  of  the  rolls.  If  we  were  to  bring  the  speed  of  the  fast  roll  to 
1000  revolutions  per  minute,  with  a  corresponding  increase  in  the  speed 
of  the  slower  roll,  the  direction  of  the  corrugations  might  be  laid  in  the 
generating  circle,  and  the  shape  adopted,  that  in  Fig.  209.  In  this  manner 
we  should  obtain  a  steady  load,  annul  the  pressure  against  the  axis,  and 
considerably  raise  the  capacity  of  the  mills.  That  is  the  reason  why 
the  question  concerning  the  preparation  of  cemented  iron  rolls  should 
receive  earnest  consideration. 

In  closing  the  chapter  on  the  inclination  of  the  corrugations,  we  must 
remark  that  it  depends  entirely  upon  the  coefficient  of  friction  of  the  pro- 
duct upon  the  material  of  the  rolls.  If  experiments  prove  that  /  for  the 
grain  is  smaller  and  increases  for  semolina  in  accordance  with  the  diminu- 
tion of  its  size,  then  the  L  a  must  likewise  gradually  increase,  as  it  clearly 
follows  from  the  formula  sin  a=tgq>  (for  the  limit  of  signification  Z=Pf), 
because  the  L  y  modifies  within  the  limits  of  12°  and  25°  maximum. 
The  inclination  of  the  corrugations,  therefore,  has  to  be  accepted  at 
10  to  16  per  cent.,  i.e.  -at  10  mm.  to  16  mm.  to  100  mm.  of  length  of 
the  roll. 

Position  of  the  Cutting  Edges  of  the  Corrugations. — The  position  of  the 
cutting  angles  of  the  corrugations  in  respect  to  the  product  treated  plays 
no  small  part  in  the  process  of  breaking  the  berry.  The  practice  of  this 
process  in  Russia  generally  recognises  but  one  position  of  corrugations, 
viz.  the  product  is  fed  in  by  the  sharp  edges  of  the  slowly  revolving  roll 
and  is  subjected  to  the  cutting  effect  of  the  likewise  sharp  edge  of  the 
fast  roll.  The  general  practice  partly  of  the  West  and  chiefly  of  America, 
has  evolved  four  types  of  position  for  corrugations. 

Those  types  are  to  be  seen  on  Fig.  211.  Here  a  shows  a  sharp  edge 
opposite  to  a  sharp  one,  b  sharp  to  dull,  c  dull  to  sharp,  and  lastly, 
d  dull  to  dull. 

The  Germans  recognise  only  three  types  of  position  of  the  corruga- 
tions, namely,  a,  b,  and  d,  while  in  America  also  the  type  c  is  used.  In 
F.  Baumgartner's  opinion  the  type  a  is  to  be  employed  for  breaking, 


CHAP,  iv]  FLOUR    MILLING  229 

type  b  for  loosening  the  bran,  and  type  d  for  rebreaking  of  pure  middlings 
("  Auflosing  "  named  "  Polishing  "  in  Russian  milling). 

The  well-known  German  factory  form.  Seek  Bros,  and  the  Austrian 
firm  of  Selmar  Hecht  (Vienna),  apply  the  one  type  a  for  the  whole  break- 
ing process. 

Let  us  examine  every  one  of  those  types  apart. 

Undoubtedly  in  high  milling  the  type  a  should  be  used  only  while 
the  break  semolina  is  sufficiently  large  and  sharp.  But  beginning  with 
the  fifth  break,  it  ought  to  be  replaced  by  the  type  6,  because  only  in 
that  case  can  a  large  quantity  of  broad  bran  be  obtained  and  the  coarse 
meal  and  middlings  be  less  dirtied  by  the  small  particles  of  reduced  bran. 

It  is  evident  that  if  the  product  is  fed  in  by  the  dull  edges,  the  sharp 
edges  of  the  fast  roll  will  scrape  out  the  middlings  without  breaking  up 
the  covers,  which  offer  greater  resistance  to  the  cutting  force. 

When  we  turn  to  the  last  break,  the  purpose  of  which  is  to  clean 
the  bran  and  separate  from  it  the  mealy  particles  of  endosperm  lying 


Fia.  211. 

immediately  beneath  the  integument,  then,  to  avoid  the  reduction  of  bran, 
it  is  reasonable  to  use  the  type  d.  The  opinion  expressed  by  Baumgartner, 
who  recommends  the  type  b  for  the  loosening  process,  is  to  be  regarded 
as  erroneous,  for  the  cutting  of  the  bran  is  inevitable  in  that  case. 

The  type  d  must  be  employed  for  polishing  the  middlings  (Aunosung), 
i.e.  the  scratch  rolls,  and  for  the  passages  following  after  the  first  one  in 
rye  milling. 

As  to  the  type  c,  it  is  used  only  in  America  partly  in  the  rye,  partly 
in  maize  milling,  mostly  for  the  first  passage.  In  several  American 
mills,  however,  wejiad  the  occasion  to  see  the  type  c  applied  to  the 
grinding  of  very  hard  wheats.  One  of  the  oldest  American  firms, 
Nordyke  &  Marmon  Co.,  in  Indianapolis,  also  mentions  the  use  of 
type  c  for  very  hard  wheats,  commencing  with  the  third  break,  though 
it  gives  no  definite  considerations  in  favour  of  that  type. 

The  Number  of  Corrugations. — The  number  of  corrugations  in  the 
breaking  passages  depends  on  the  degree  of  perfection  of  the  milling. 
In  high,  protracted  milling  the  number  of  corrugations  increases  more 
slowly  than  in  the  semi-high.  In  the  cases  where  one  is  obliged  to  use 


230  FLOUR   MILLING  [CHAP,  iv 

the  same  pair  of  rolls  for  two  passages  (as  in  the  sack  milling  or  in  the 
semi-automaton),  an  intermediate  number  of  corrugations  is  taken. 

The  number  of  corrugations  is  generally  denned  to  a  centimetre  of 
the  circumference  of  the  roll ;  in  Russia,  however,  the  number  of  corru- 
gations is  generally  given  per  inch. 

The  table  adduced  below  gives  a  general  view  of  the  number  of 
corrugations  for  breaking  and  cleaning  of  the  bran  (the  last  passage) 
in  different  kinds  of  milling.  There  the  average  numbers,  evolved  by 
practice,  are  given.  In  the  same  table  will  be  pointed  out  the  desk-able 
inclination  of  the  corrugations  and  the  position  of  their  cutting  edges 
according  to  the  above-mentioned  types. 

This  table  must  be  regarded  as  giving  the  normal  quantity  of  corru- 
gations to  a  given  number  of  breaks.  As  the  number  of  breaking 
passages  fluctuates,  according  to  the  type  of  the  grinding  or  the  hard- 
ness of  the  wheat,  the  number  of  corrugations  on  the  intermediate 
breaks  may  vary.  The  first  and  the  last  breaks,  however,  have  to 
retain  the  mentioned  numbers  of  corrugations,  if  it  is  desirable  to  obtain 
broad  bran.  For  the  first  break  (if  there  is  no  "  Hochschrot,"  i.e.  break- 
ing of  grain  along  the  crease)  there  remain  three  to  four  corrugations  to 
a  centimetre,  and  for  the  last  twelve  corrugations. 

It  must  be  noted  that  we  considered  the  number  of  corrugations  in 
connection  with  the  generally  accepted  differential  velocity  of  rolls,  and 
with  the  normal  number  of  revolutions  for  the  fast  roll,  established  by 
German  and  English  factories  and  based  on  the  normal  productivity  of 
the  breaking  process.  For  this  reason  we  give  tables  of  different  types 
of  grinding  here,  which  also  characterise  the  definite  productivity  of  the 
breaking  process  in  connection  with  the  accepted  corrugating. 

From  this  table  we  learn  that  for  high  grinding  (eight 
breaks  without  "  Hochschrot ")  with  a  normal  number  of  corruga- 
tions and  spiral,  the  joint  working  length  of  the  break  rolls  to 
one  sack  of  grist  per  day  is  defined  to  be  21-24-7  mm.  To  obtain  the 
length  of  the  first  break  rolls  for  a  mill  of,  for  instance,  300  sacks  capacity 
of  high  grinding  per  twenty-four  hours,  we  must  evidently  multiply 
2-7-3  mm.  by  300.  That  will  give  us  the  length  of  the  rolls  for  the  first 
break,  which  will  be  810  to  900  mm.  in  eight  breaking  passages.  This 
being  the  length,  the  general  incline  of  the  corrugations  is  120  mm. 

For  medium  grinding,  with  a  normal  number  of  corrugations  and 
their  incline,  the  joint  working  length  of  the  break  rolls  to  one  sack 
of  grist  per  day  is  19" 8-22 -3  mm.,  for  low  grinding  17*9-20  mm.,  and 
lastly  23*3-24-5  mm.  for  English  grinding. 


CHAP.   IV] 


FLOUR   MILLING 


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[CHAP.  IV 


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CHAP,  iv]  FLOUR   MILLING  233 

Consequently,  with  a  normal  number  of  inclined  corrugations,  the 
following  capacity  is  denned  for  four  kinds  of  grist  (in  Ibs.)  to  a  centimetre 
or  an  inch  of  the  working  length  of  all  the  breaking  passages  per  twenty- 
four  hours : 

TABLE    XXIV 

CAPACITY  OF  THE  ROLLS  PER  TWENTY-FOUR  HOURS  TO  1  CM.  OR 

1  INCH  IN  LBS. 


Kind  of  Grinding. 

Per  1  cm.  of  Length 
of  the  Roll. 

Per  1  inch  of  Length 
of  the  Roll. 

High  grinding 
Medium   „ 
Low         „             ... 
English    „             ... 

Ibs. 

107-125 
122-135 
134-153 
97-117 

Ibs. 

268-313 
302-336 
333-382 
243-302 

But  as  the  capacity  of  the  breaking  process  is  defined  by  the  absolute 
and  differential  velocity  of  the  rolls,  the  number  of  corrugations  and 
the  other  elements  characterising  the  corrugating  (their  inclination  and 
position)  were  dealt  with  in  connection  with  the  generally  accepted 
velocities  of  the  rolls  :  the  absolute  velocity  of  rotation  of  the  rolls  is 
3*  5-4 '5  metres  per  second,  and  the  ratio  of  velocity  of  the  slow  and  fast 
rolls  is  1 :  2'5-l :  3. 

Here  we  may  close  our  investigation  of  the  question  concerning  the 
corrugating  of  rolls.  All  that  has  been  said  proves  that  this  question, 
which  opens  out  a  new  line  of  thought,  as,  for  instance,  of  the  shape  of 
the  grooves  in  connection  with  the  investigation  of  the  process  of  break- 
ing, demands  serious  experimental  treatment. 

Since  the  time  of  Professor  F.  Kick  and  K.  A.  Zworykin — in  the  course  of 
almost  twenty  years — this  question  has  not  stirred  from  its  place,  whereas 
in  other  regions  of  mechanical  technology  we  witness  gigantic  progress. 

3.  Adjustment  of  the  Distance  between  the  Working  Surfaces 

The  degree  of  reduction  of  the  product  depends  not  only  on  the  form 
(corrugated  or  smooth)  but  also  on  the  distance  between  the  working  surfaces. 
In  accordance  with  the  size  and  the  hardness  of  the  product,  it  is  neces- 
sary to  alter  the  distance  between  the  break  rolls  with  the  view  of  obtain- 
ing the  quantity  of  coarse  and  fine  middlings  given  in  the  plan,  as  the 
machines,  which  divide  the  product  according  to  its  quality  (purifiers), 
are  calculated  for  a  certain  quantity  and  size  of  this  product.  For 
this  reason  every  roller-mill  must  be  furnished  with  a  mechanism  which 
will  afford  the  possibility  of  adjusting  the  distance  between  the  rolls 


234 


FLOTJK   MILLING 


[CHAP,  iv 


at  any  moment.  The  necessity  of  adjusting  the  distance  is  likewise 
evident  in  the  case  of  smooth  rolls,  on  which  coarse  and  fine  middlings 
of  various  sizes  have  to  be  reduced,  and  meal  of  different  fineness 
obtained.  The  possibility  of  adjusting  the  distance  between  the  rolls 
can  be  attained  by  making  only  one  of  them  adjustable,  so  as  not  to 
complicate  the  construction  of  the  machine. 

The  adjusting  mechanisms  are  named  "brakes."  x  As  it  is  impossible 
to  reckon  upon  an  ideal  freeing  of  the  grain  of  metal  admixtures  before 
milling,  and  there  is  also  the  possibility  of  their  dropping  in  out  of  the 
machinery  during  grinding,  the  construction  of  the  brake  must  be  such, 
that  in  case  of  a  nail  or  any  other  metal  object  falling  in,  the  surface 
of  the  rolls  shall  not  become  spoilt,  or  the  driving  organs  of  the  machine 


FIG.  212. 

break.    The  brakes  satisfying  those  requirements  are  called  tension  brakes. 

We  shall  explain  the  idea  of  the  tension  brake  on  schematic  con- 
structions. 

On  Fig.  212  we  have  four  sketches  of  tension  brakes.  Sketch  1 
exhibits  the  form  of  the  simplest  brake.  The  roll  B  is  set  in  stationary 
bearings  D  fixed  in  the  frame  C  of  the  mill.  The  roll  A  lies  in  bearings  E, 
which  may  be  displaced  to  the  right  and  to  the  left  within  the  slippers 
P-P*  of  the  frame.  If  the  rolls  are  to  be  set  at  a  certain  distance,  the 
bolts  I,  screwed  into  the  frame  with  their  threaded  part  and  their  conic 
heads  resting  against  the  adjustable  bearing  E,  are  turned.  With  the  aid 
of  these  bolts  also  the  evenness  of  the  axes  of  the  rolls  may  be  adjusted. 
From  the  opposite  side,  the  bearings  are  pressed  by  the  springs  k,  resting 

1  This  term  is  used  throughout  the  work  to  denote  what  is  now  generally  termed  hi  England 
"adjustment  mechanism"  or  "adjustments."  It  is  short,  and  correctly  expresses  what 
otherwise  entails  needless  circumlocution. 


CHAf.  iv]  FLOUR   MILLING  235 

on  the  collars  of  the  bolt  a  screwed  into  the  hub  b  with  a  corresponding 
thread.  In  this  manner  we  have  obtained  the  desired  distance  between 
the  rolls  and  a  definite  grade  of  pressure  upon  it  by  the  spring  k.  If  a 
piece  of  iron  that  the  rolls  cannot  break  down  passes  in  between  them, 
the  pressure  is  communicated  to  the  journals  of  the  rolls.  Now,  as  the 
spring  is  calculated  to  withstand  a  certain  utmost  strain  for  the  reduc- 
tion of  the  product,  whereas  the  pressure  of  the  metal  particle  exceeds  it, 
the  springs  acted  upon  by  this  pressure  will  contract  and  the  bearings  E 
move  to  the  left.  The  widened  space  between  the  rolls  allows  the  metal 
particle  to  pass  through  without  damaging  the  machine,  after  which  the 
spring  pushes  the  bearings  back  into  their  former  position. 

To  adjust  the  tension  of  the  springs  the  bolts  a  are  screwed  in  or  out 
by  means  of  a  hand-wheel  M .  To  prevent  the  screwing  out  of  the  bolts 
a,  there  are  nuts  with  wings  M j  on  the  outside,  serving  as  lock-nuts. 

The  type  of  brake  just  examined  has  the  defect,  that  it  requires  a 
complicated  mechanism  for  the  throwing  out  of  the  rolls,  as  the  adjustable 
bearings  move  rectilinearly.  Therefore  the  brakes  shown  on  sketches 
//,  ///,  and  IV  are  more  rational  types  of  construction.  The  right-hand 
roll  of  all  those  constructions  is  adjustable.  Its  adjustable  bearing  A 
is  set  in  a  movable  arm  B,  which  has  a  stationary  axis  of  rotation  0.  The 
other  end  of  the  arm  rests  on  the  spring  (7,  which  may  be  adjusted  as  in  the 
first  case.  On  the  side  opposite  to  the  spring  there  is  set  a  lever  D  with 
an  eccentric  on  a  stationary  axis  0±.  The  springs  in  the  //  and  ///  plans 
are  compressed  by  the  end  of  the  arms  B,  and  stretched  in  the  /Fth. 
Plan  //  represents  a  lever  of  the  first  order,  and  the  plans  ///  and  IV 
levers  of  the  second  order.  The  advantage  of  these  three  designs  lies  in 
the  fact  that  owing  to  the  pressure  being  transmitted  through  levers, 
there  is  no  need  of  a  spring  so  strong  as  in  plan  /. 

To  throw  out  the  rolls  it  is  sufficient  to  turn  the  lever  D  as  pointed 
by  the  arrow  S.  During  the  run  of  the  rolls  "in  gear"  the  lever  D  is 
fastened  by  various  means,  to  be  examined  later.  The  construction  of 
the  brakes  on  these  plans  may  be  infinitely  varied  according  to  the 
type  of  mills. 

Besides  the  spring  brakes  there  have  been  suggested  constructions  where 
the  spring  is  replaced  by  a  weight.  The  plan  of  one  of  such  brakes, 
corresponding  to  the  second  spring  plan,  is  shown  in  Fig.  213.  The 
spring  is  replaced  here  by  a  crank  mechanism  with  a  weight  G,  rotating 
on  a  rigid  axle  d2.  The  setting  of  the  rolls  at  the  distance  required,  and 
the  dressing  of  the  parallelity  of  their  axes,  is  done  by  means  of  the  bolts 
s  and  Sj.  When  the  pressure  upon  the  adjustable  roll  b  exceeds  the 


236 


FLOUR   MILLING 


[CHAP,  iv 


normal,  the  deflecting  tail  n  of  the  lever  transmits  the  pressure  to  the 
crank  mechanism  through  the  bolt  sl3  and  after  the  hard  particle  has 
passed  between  the  rolls  the  weight  G  brings  the  roll  to  its  established 
position. 

From  time  to  time  the  inventors  patent  such  weight  brakes.  But 
we  must  say  that  this  bulky  appliance  offers  no  advantages  in  compari- 
son to  the  spring  brake  and  at  the  same  time  complicates  the  construction 
of  the  roller  mill ;  for  this  reason  such  makes  ought  to  be  rejected. 

As  regards  the  first  design,  it  is  to  be  met  with  in  the  simplest 
American  mills  for  crushing  hard  materials  (quartz,  &c.).  Of  the  roll 
sets  for  mills  there  is  known  only  one  American  construction  of  Noye's 


FIG.  213. 


FIG.  214. 


in  Buffalo,  who  very  unsuccessfully  adapted  the  principle  of  direct  action 
of  the  pressure  of  the  spring  (Fig.  214).  The  resistance  of  the  spring  here 
is  placed  below  the  axes,  therefore  the  pressing  force  P  gives  a  vertical 
component  Fj  and  a  couple  Th,  which  causes  friction  of  the  bearings  in 
the  guide  parallels.  It  is  only  the  component  F,  directed  to  the  left, 
that  transmits  the  pressure  to  the  spring.  For  this  reason  the  mechanism 
must  be  less  sensitive. 


4.  A  General  Survey  of  the  Roller  Mill 

To  understand  the  meaning  and  importance  of  the  details  of  the  roller 
mill  one  ought  previously  to  become  acquainted  with  the  general  character 
of  its  construction,  where  those  details  may  be  seen  and  their  purpose 
understood.  For  this  purpose  we  shall  inspect  the  construction  of  the 
four-roller  mills,  for  those  mills  represent  double  two-roller  mills  and 
constructionally  in  no  way  differ  from  the  twin  rollers  set  in  separate 
frames. 


CHAP.    IV] 


FLOUR    MILLING 


237 


Roller  Mill  of  Ganz  &  Co.  in  Budapest. — Fig.  215  illustrates  Ganz's 
roller  mill  in  section.  Let  us  examine  the  right-hand  half  of  this  mill. 
The  product  flows  into  the  hopper  b  of  the  mill,  with  its  weight  presses 
open  the  gate  w,  and  falls  upon  the  feeding  rolls  which  are  rotating  in  the 
direction  of  the  clock  hand.  With  the  view  of  letting  through  these  rolls 
a  stream  of  product  of  the  desired  thickness  there  is  a  gate  down  the  whole 
length  of  the  hopper,  which  may  be  opened  more  or  less  by  means  of  a 


FIG.  215. 

hand- wheel  h.  From  the  feeding  rolls  the  stock  runs  to  the  reduction 
rolls,  and  on  passing  between  them  falls  through  the  hopper  a  into  the 
spout.  During  the  milling  of  a  moist  product  there  is  the  possibility  of 
its  sticking  to  the  surface  and  blinding  the  corrugations,  and  therefore, 
under  the  rolls  down  their  full  length  there  are  scrapers  set  (knives  for 
the  smooth,  brushes  for  the  corrugated  rolls)  to  free  them  of  the  adhering 
particles. 

For  the  inspection  of  the  feed  there  is  a  gate  opposite  to  the  feed 
rolls,  and  another  one,  for  inspecting  the  operation  of  the  rolls,  is  set  in 


238 


FLOUR   MILLING 


[CHAP,  iv 


the  frame  below  the  rolls.  Through  both  of  them  at  any  moment  the 
stock  may  be  seen  and  reached  with  the  hand  on  opening  the  gate. 

Let  us  see  now  how  the  problem  of  adjusting  the  distance  between 
the  working  surfaces  is  solved  here. 

In  modern  mills  the  regulation  of  the  working  distance  and  the 
mechanism  for  throwing  the  rolls  out  of  gear  are  joined  in  one  common 
construction.  When  the  mill  is  in  working  order  the  gate  w  is  either  in  a 
vertical  position  or  inclined  to  a  certain  degree,  which  depends  on  the 
quantity  of  the  product  fed.  The  gate  w  rotates  on  an  axis,  which  has  a 
lever  on  the  outside  (Fig.  217)  with  a  weight  z  counterbalancing  the 


FIG.  216. 

pressure  of  the  grain  upon  the  gate  w.  This  lever  is  joined  by  means 
of  a  finger  with  another  lever  y  with  the  axis  of  rotation  at  the  side 
of  the  feed-hopper. 

On  the  right-hand  side  of  the  lever  y  there  is  a  cavity  for  the  finger  of 
the  handle  of  the  lever  x  (Fig.  218)  leading  to  the  rod  r  of  the  brake  M 
(Fig.  217).  The  lever  x  is  set  on  the  roll  u  which  runs  through  the  whole 
length  of  the  mill.  The  end  of  the  lever  x  is  connected  by  a  rod  r  with 
the  brake  or  adjustment  mechanism  proper,  the  joint  being  of  the  ball 
and  socket  kind. 

The  brake  corresponds  to  our  fourth  plan.  Its  construction  is  as 
follows.  In  the  levers  M  which  have  their  axis  of  rotation  in  N,  there 
are  held  by  means  of  screws  g  the  bearings  of  the  slowly  revolving  side 
rolls  d  and  dv  These  same  bolts  afford  the  possibility  of  setting  the  axes 


CHAP.    IV] 


FLOUR   MILLING 


239 


I! 


240 


FLOUR   MILLING 


[CHAP,  iv 


of  the  rolls  horizontally.  The  top  end  of  the  lever  M  (Fig.  219)  is  a  ten- 
sion brake  of  the  following  construction.  The  hub  of  the  lever  contains 
a  spring  c,  resting  on  the  right-hand  side  against  the  washer  m  which  is 
screwed  to  the  hub,  and  on  the  left  against  the  ring  n.  Through  the 
hub  there  freely  runs  the  bolt  o  joined  with  the  rod  r.  If  a  hard  object  is 
caught  in  between  the  rolls  and  the  pressure  exceeds  the  normal,  the  hub 
of  the  lever  transmits  the  pressure  through  the  washer  m  to  the  spring  c, 
and,  compressing  the  spring,  moves  to  the  left,  and  when  the  hard  object 
has  passed  the  working  area  of  the  rolls,  the  spring  compels  the  lever  to 
return  to  its  former  position.  The  tension  of  the  spring  is  increased  by 
turning  the  hand-wheel  h,  the  square  pin  j  having  been  previously  pressed 
in  and  stopped  by  screw  k. 

We  shall  now  examine  the  operation  of  the  whole  mechanism.     To 


FIG.  219. 

bring  the  rolls  into  working  position,  we  must  lift  the  lever  x,  which  with 
its  pin  raises  the  lever  y  and  the  lever  with  a  weight  z  (Figs.  217  and  218). 
Then  the  gate  w  drops  and  the  product  flows  to  the  feed  rolls.  With  its 
weight  the  product  keeps  back  the  gate  and  prevents  the  weight  z  from 
disjoining  the  levers  x  and  y.  As  soon  as  the  flow  of  the  product  into 
the  hopper  is  stopped,  the  pressure  upon  the  gate  w  is  removed,  and  the 
weight  z  will  drop  down,  lift  the  lever  y,  and  disengage  it  with  x.  Then, 
acted  upon  by  the  springs  of  the  brake,  the  levers  M  will  force  the  bearings 
apart.  But  as  there  is  the  possibility  of  the  grain  recommencing  to  flow 
from  the  hopper,  there  must  be  arranged  an  adjustment  to  retain  it 
there.  For  this  purpose  each  mill  is  supplied  with  a  mechanism  stop- 
ping the  action  of  the  feed  rolls,  which  in  Ganz's  mill  is  effected  in  the 
following  manner.  The  axle  u,  connecting  the  brakes  of  the  roll,  carries 
pn  a  key  a  hub  with  the  lever  A  (Fig.  219)  which  is  connected  by  means  of 


CHAP.   IV] 


FLOUR    MILLING 


241 


levers  B  and  C  with  the  hub  c,  freely  running  on  a  key  of  the  axle  F  of 
the  bottom  feed  roll.  The  left-hand  part  of  the  coupling  is  furnished 
with  cross-heads.  On  the  end  of  that  same  roll  there  is  a  freely  rotating 
belt-pulley  with  a  jutting  out  pin  and  a  hub  which  also  ends  in  cross- 
heads  corresponding  to  those  of  the  hub  c.  A  bell  is  attached  to  the  end 
of  the  roll  F.  When  the  machine  is  set  operating  the  axle  u  turns  so 
that  the  levers  A,  B  and  C  push  the  hub  c  to  the  left  and  bring  it  with  its 
cross-head  end  into  connection  with  the  hub  of  the  belt-pulley.  Then 
the  feed-roll  also  commences  rotating.  As  soon  as  the  mill  runs  empty, 
the  hub  c  becomes  disengaged  with  the  hub  of  the  belt-pulley,  which 
from  this  moment  freely  rotates  on  the  now  stationary  roll  F.  The 
pin  of  the  belt-pulley  hits  the  spring  with  the  small  hammer,  which 
having  got  loose  at  a  certain  part  of  the  turn,  hits  the  bell.  This  serves 


FIG.  220. 

as  a  signal  that  there  is  no  stock  in  the  machine.  The  spring  is 
attached  on  the  hub,  which  is  pressed  to  the  shoulder  on  the  end  of 
the  axle. 

A  detail  of  the  adjustable  bearing  is  illustrated  on  Fig.  220.  Here 
the  box  a  of  the  bearing  has  a  cavity  for  the  stopping  and  adjusting  bolts 
</,  b  is  a  bronze  bush,  c  the  oil  chamber,  and  /  the  canal  for  the  exhausted 
oil  to  c.  The  bearing  has  ring  lubrication. 

The  Seek  Bros.  Roller  Mill. — Let  us  examine  the  Seek  Bros,  mill, 
which  has  diagonally  placed  rolls  (Fig.  221).  The  product  is  fed  into 
the  box  V,  divided  into  two  parts  by  a  timber  partition. 

As  in  the  preceding  machine,  both  parts  of  this  mill  can  reduce  the 
same  or  a  different  kind  of  product,  as  each  pair  of  rolls  constitutes  an 
independent  machine.  The  axis  of  rotation  w  of  the  lever  of  the  upper 
bearing  is  at  the  top.  The  adjustable  top  roll  is  put  in  gear  by 
hand  with  the  aid  of  a  lever  B,  which  is  brought  to  its  highest  position 

9- 


CHAP,  iv]  FLOUR    MILLING  243 

for  that  purpose,  and  raises  the  flat  lever  C,  which  drops  the  gate  D 
for  the  inflow  of  the  product.  By  means  of  an  automatic  displace- 
ment of  the  cross-head  coupling,  the  feed  rolls  are  simultaneously 
brought  into  motion.  The  throwing  out  of  the  roll  is  performed 
automatically,  as  soon  as  the  flow  of  the  grain  into  the  hopper  is  dis- 
continued. Meeting  no  resisting  pressure  of  the  stock,  the  gate  D,  owing 
to  the  counterbalance,  assumes  a  horizontal  position,  freeing  the 
engagement  of  the  lever  C,  and  through  the  action  of  the  spring  E 
(Fig.  221)  the  simultaneous  disjunction  of  the  reduction  and  of  the  feeding 
rolls  is  brought  about. 

The  mechanism  for  the  adjustment  of  the  distance  between  the  rolls  is 
operated  by  a  hand  wheel  G.  For  setting  the  spring  brake  encased  in  a 
box  J,  there  is  the  nut  K .  For  balancing  the  counterweight  of  the  gate  D 
the  screw  rod  S  is  connected  by  a  spring  R  with  the  lever  of  the  counter- 
weight. 

When  in  working  position  the  gate  D  is  dropped.  The  product  flows 
into  the  roller-feeder.  The  gate  0  gives  a  wider  or  narrower  passage, 
being  removed  from  the  top  roll  or  approached  to  it  by  the  screw-rods  T 
and  P.  Under  the  rolls  there  is  placed  a  plate  M  on  which  the  heavy 
(metal)  particles  collect.  The  stock  thrown  from  the  first  roll  on  to  the 
second  falls  from  the  latter  on  the  inclined  plate  X  and  is  passed  to  the 
working  space  of  the  rolls.  For  removing  the  particles  of  product  stick- 
ing to  the  rolls  and  blinding  the  corrugations,  there  are  brushes  fitted, 
or,  as  in  this  case,  for  smooth  rolls,  scrapers  d  and  b. 

The  perspective  view  of  the  Seek  Bros,  mill  is  shown  on  Fig. 
222. 


5.  The  Feeding  of  the  Rolls 

An  examination  of  these  two  mills  gives  us  an  idea  as  to  the  char- 
acteristic details  pertaining  to  such  machines  in  regard  to  the  feed  and 
the  brake  or  adjustment  mechanism.  The  quality  of  the  work  of  the 
machine  depends  on  the  successful  construction  of  those  mechanisms,  and 
therefore  it  is  necessary  attentively  to  study  the  various  types  of  the  feed 
and  the  brake  devices  existing. 

The  working  surfaces  will  yield  a  uniform  grist  only  if  the  stock  flows 
to  the  rolls  in  a  continuous  sheet  of  equal  thickness  down  the  full  length 
of  the  working  surfaces.  If  the  product  runs  not  in  a  continuous  film 
but  in  separate  streams,  firstly  a  part  of  the  working  surface  will  be  in 
disuse,  and  secondly  the  thick  streams  of  grain,  not  calculated  to  answer 


244 


FLOUR    MILLING 


[CHAP,  iv 


the  definite  space  between  the  working  surfaces,  will  cause  a  strong  pres- 
sure, and  widen  this  space,  thus  allowing  the  product  to  pass  through 
partly  unreduced.  In  the  process  of  reducing  the  semolinas  and  middlings 


FIG.  222. 


the  feeding  of  the  product  in  streams  results  in  a  great  quantity  of  flakes, 
and  makes  the  flour  dead. 

The  feeding  mechanism  will  perform  its  work  correctly  if  the  follow^ 
ing  requirements  are  satisfied  ; 


246 


CHAP,  iv]  FLOtm   MILLING 

(1)  An  even  and  continuous  flow  of  the  product. 

(2)  Automatic  regulation  of  the  flow. 

(3)  The  shortest  way  from  the  feeding  mechanism  to  the  rolls. 

(4)  Absence  of  any  obstructions  to  the  flow  of  the  product. 

Let  us  examine  now  all  the  existing  types  of  feeding  devices 
and  give  an  estimation  of  them  from  the  point  of  view  of  the  stated 
requirements. 

Fig.  223  represents  a  mill  with  diagonally  set  rolls.     The  product 


FIG.  223. 

flows  into  the  feeder  A  and  with  its  weight  presses  upon  the  gate  ri,  hold- 
ing the  counterweight  /  off  (on  the  other  side  of  the  machine).  The  gate  t 
is  set  at  the  greatest  desired  opening  between  its  edge  and  the  feed  roll  4 
with  the  aid  of  screws  1  and  stops  3.  Sometimes  spring  stops  are  employed, 
and  their  number  is  from  two  to  four,  according  to  the  size  of  the 
machine.  The  gate  t  is  fixed  to  a  square  stem  6  with  journals,  one  of 
which  protrudes  out  of  the  box  and  carries  on  a  key  a  lever  7  held  back 
by  screw  rod  2  with  a  spring.  The  feed  rolls  are  covered  from  below  by  a 
screen  9  to  catch  up  the  product  accidentally  passing  between  them. 
When  the  inflow  of  the  stock  to  A  diminishes,  the  spring  8  pulls  the  lever 


246  FLOUR   MILLING  [CHAP,  iv 

6  and  turns  the  gate  t  to  the  left,  owing  to  which  the  space  between  the 
feeding  roll  4  and  its  edge  diminishes.  The  degree  of  stability  of  the  gate  t 
is  regulated  by  the  greater  or  smaller  tension  of  the  spring  8,  which  is 
obtained  by  means  of  a  nut  2,  which  may  be  screwed  up  more  or  less. 
The  product  passed  from  the  roll  4  to  5  along  the  arrow  $x  falls  on  the 
screen  r,  then  on  the  top  roll  and  the  screen  q,  which  carries  it  to  the  slowly 
rotating  bottom  roll. 

When  the  stock  ceases  to  flow  into  the  feeder  A  the  weight  /  drops 
down  and  closes  the  gate  n.  In  this  manner,  as  it  is  in  Ganz's  mill, 
the  rotation  of  the  feed-rolls  is  discontinued  and  the  adjustable  roll  is 
thrown  apart  from  the  top  one.  It  may  be  noticed,  by  the  way,  that  the 
brake  device  here  is  based  on  the  same  principle  as  that  of  Ganz's,  but 
slightly  complicated  by  a  third  axis  of  bearing  Oj. 

Before  proceeding  to  the  estimation  of  roller  feeding,  we  shall  examine 
a  series  of  analogous  constructions,  but  for  the  moment  we  must  direct 
our  attention  to  the  main  detail  of  the  mechanism,  the  feed-rolls.  We 
have  seen  two  feeding  rolls  in  the  construction  examined.  The  first 
one,  4,  is  named  the  supplier,  the  second,  5,  the  feeder.  They  are  brought 
into  rotation  by  belt-gearing  from  the  belt-pulleys  N  on  the  axes  of  the 
rolls  with  stationary  bearings.  The  number  of  revolutions  of  the  supply- 
ing roll  4  generally  varies  between  thirty  and  forty-five  per  minute,  and 
that  of  the  feeder  5  is  three  to  four  times  greater.  Their  diameters  are  : 
120-160  mm.  of  the  larger  roll,  and  60-80  mm.  of  the  smaller,  which  cor- 
responds to  the  circumferential  velocities  up  to  0'33  metres  per  second 
for  the  first,  and  up  to  0'75  metres  per  second  for  the  second.  The 
European  factories  maintain  that  the  flow  of  stock  is  less  even  when  sup- 
plied by  one  feed  roll  only,  especially  when  the  product  is  soft,  and  at 
the  same  time  most  of  the  factories  recommend  feed  rolls  of  different 
diameters,  as  in  the  case  just  dealt  with.  The  Americans  are  of  a  different 
opinion,  and  prefer  the  use  of  one  feed  roll,  or  even  totally  avoid  roller- 
feeding,  as  we  shall  see  later. 

In  our  turn  we  must  remark  that  both  the  European  and  the  American 
methods  of  feeding  give  very  satisfactory  results.  Everything  depends, 
as  observations  prove,  on  the  choice  of  a  suitable  velocity  of  rotation  of 
the  feed  rolls  or  the  number  of  vibrations  of  the  American  feeding 
plates,  and  upon  the  loading  of  the  feeder  A  also. 

Returning  to  the  roller-feeding,  we  must  give  an  idea  as  to  the  con- 
struction of  the  rolls. 

The  feeding  rolls  are  hollow,  cast-iron  cylinders  with  corrugations 
cut  parallel  or  perpendicularly  to  their  axis.  There  are  three  shapes  of 


CHAP,  iv]  frLOUR   MILLING  247 

corrugations  used  :  (1)  with  sharp  angles  (Fig.  224),  (2)  of  a  semicircular 
shape  in  section  (Fig.  225),  and  (3)  the  shape  of  an  isosceles  triangle  in 
section,  when  the  corrugations  are  cut  along  the  circumference  of  the 
roU  (Fig.  227). 

The  corrugations  shown  in  Figs.  224  and  225  of  the  given  dimensions 
are  cut  on  the  first  feed  rolls,  and  those   of  the  dimensions  shown  on 


FIG.  224 


FIG    225 


FIG.  227. 


Figs.  226  and  227  on  the  second,  if  two  rolls  are  employed  for  the  feeding. 
The  axes  of  the  rolls  are  set  diagonally,  and  the  angle  of  inclination 
depends  on  their  circumferential  velocities  and  distance  from  the  grinding 
rolls.  The  distance  between  the  axes  of  the  roUs  is  generally  less  than 
the  semi-total  of  their  diameters,  but  in  some  mills,  as  will  be  seen  later, 
it  considerably  exceeds  that  quantity. 

In  giving  an  estimate  of  the  shape  and  position  of  the  corrugations, 
it  will  be  as  well  to  say  that  the  transversal  corrugations  lately  suggested 
by  the  firm  of  H.  Simon  in  Manchester 
must    certainly    not    be    used,    as    they 
break  up  the  solid  sheet  of  product  into 
streams. 

Fig.  228  illustrates  a  single  roll  feed 
ing,1  to  which  we  shall  direct  our  attention 
with  the  view  to  explaining  several  details 
of  the  setting  of  rolls. 

The  feed-hopper  A  of  the  mill  ends  in  a 
trough- shaped  shoe  B  which  can  turn  on 
the  axis  o.  The  feed  of  the  stock  is 

regulated  by  a  sliding  gate  p.  The  distance  between  the  feeding  roll  w  and 
the  shoe  is  adjusted  by  means  of  cross-heads  n,  by  turning  them  to  the  right 
.or  to  the  left.  To  prevent  the  product  from  passing  between  the  wall 
of  the  feeder  and  the  shoe,  the  latter  is  furnished  with  a  flange  z.  For 
inspecting  the  feeding  operation  there  is  a  door  C.  The  main  point  of 
this  construction  lies  in  the  trough-like  form  of  the  shoe,  which  is 
designed  to  collect  the  heavy,  mostly  metal,  extraneous  matter  fallen  to 
the  bottom  owing  to  its  weight,  which  exceeds  the  weight  of  the  grain. 

1  German  patent,  No.  38,184,  of  Engineer  Kaufmann,  1885. 


FIG.  228. 


FLOUR   MILLING 


[CHAP.  IV 


This  idea  has  been  utilised  in  many  modern  makes,  but  is  errone- 
ous in  its  principle,  for  the  mass  of  the  product  below  the  plane  db 
becomes  rapidly  compact,  and  therefore  the  heavy  particles  are  caught 
up  by  the  feeding  roll.  Besides  that  the  feeding  mechanism  ought  not 
to  be  forced  to  fulfil  the  duties  of  a  magnet  apparatus,  as  all  universality 
complicates  the  construction  to  the  disadvantage  of  its  prime  intention. 

We  shall  now  proceed  to  consider  further  makes  of  feeding 
devices. 

Two-roller  Feeding. — The  English  machine-building  factory  of  E.  R.  and 
F.  Turner  in  Ipswich  was  one  of  the  first  to  invent  a  rational  construction 


FIG.  229. 

of  a  diagonal  mill.  Fig.  229  illustrates  the  feeding  of  the  "  Diagonal  " 
mill  in  its  modern  form.1 

The  grain  or  the  grist  flows  into  the  hopper,  in  which  there  is  freely 
suspended  on  ball-and-socket  joints  an  iron  gate  A,  as  a  second  longi- 
tudinal wall  of  the  feed.  A  second  gate  B  directs  the  product  to  the  first 
feed-roll  N.  This  gate  may  be  approached  to  or  removed  from  the 
feeding  roll  with  the  aid  of  a  screw  E  and  nut  C  by  pressing  E  upon  the 
lever  Z>,  owing  to  which  the  flow  of  grain  increases  or  decreases. 

In  the  lever  G  there  is  a  cross-head  and  guide  which  changes  the  posi- 
tion of  the  gate  A  within  the  space  marked  K  and  Q,  when  the  spring  L 
is  pressed  by  the  nut  J. 

The  first  feed  roll  N  up  to  100  mm.  in  diameter  runs  at  about  fourteen 
revolutions  per  minute  ;  it  is  provided  with  longitudinal  corrugations 

1  English  patent,  Nos.  6501  and  11,992. 


CHAP,   ivj 


FLOUR   MILLING 


249 


of  different  sizes,  to  answer  the  definite  purpose  of  the  roller  mill  for 
breaking,  the  grinding  of  middlings,  or  cleaning  the  bran. 

The  duty  of  the  second  feeding  roll,  making  150  revolutions  per 
minute,  is  to  supply  the  stock  to  the  grinding  rolls,  which  is  done 
by  means  of  a  plate  between  the  roll  0  and  the  bottom  slowly 
rotating  roll. 

The  second  feeding  roll  is  brought  into  motion  from  a  belt-pulley  on 


FIG.  230. 

the  axis  of  the  bottom  roll,  by  transmitting  the  motion  to  the  roll  N 
through  toothed  wheels.  Both  the  rolls  are  of  the  same  diameter. 

G.  Luther's  factory  in  Brunswick  gives  a  construction  of  the  feeding 
device  (Fig.  230)  totally  different  from  the  ordinary  type,  in  that  the 
supplying  and  the  feeding  rolls  are  removed  from  each  other  by  a  consider- 
able distance. 

The  feed  is  thrown  out  of  the  hopper  by  the  roll  C  on  to  the 
plate  /,  which  together  with  the  vertical  partition  forms  a  kind  of 
second  hopper.  From  this  second  hopper  the  roll  d  carries  the  stock 
to  the  slowly  rotating  bottom  roll  a.  Thus  the  characteristic  peculiarity 


250 


FLOUR   MILLING 


[CHAP,  iv 


of  this  construction  is  the  division  of  one  hopper  into  two  parts  and  the 
absence  of  the  supplying  plate  between  the  feeding  roll  d  and  the  reduc- 
tion rolls.  The  adjustment  of  the  feeding  by  means  of  the  gate  e  is  a  very 
common  combined  construction  of  the  feeding  mechanisms  already 
examined. 

The  European  constructors  have  lately  begun  to  attach  great  im- 
portance to  improvements  in  the  regulation  of  the  flow  of  the  stock 
by  means  of  a  gate  in  the  hopper,  and  have  a  tendency  to  discard  the 
supplying  plates.  This  is  of  great  consequence,  and  we  shall  speak  of  it 
when  giving  an  estimate  of  the  various  types  of  feeding. 

On  Fig.  231  we  have  H.  Bruner's  feeding  construction  without  a 
supplying  plate,  which  operates  as  follows.1  The  feed  rolls  2-2  have  the 

same  diameter,  90  to  100  mm.  The 
top  roll  rotates  with  the  speed  of 
40-50  revolutions  per  minute,  and 
the  one  at  the  bottom  90-150,  which 
depends  on  the  product  (grain, 
semolina,  middlings,  or  bran)  for 
which  the  mill  has  been  fitted. 
Under  the  rolls  there  is  a  trough 
for  collecting  the  heavy  and  hard 
extraneous  matter.  The  gate  3  is 
adjusted  with  the  aid  of  crank 
mechanisms  and  a  spring  10.  The 
axis  of  rotation  of  the  gate  is 

marked  24.  The  crank  lever  7  revolving  round  its  axis,  when  drawn 
off  by  the  spring  10  presses  the  gate  with  its  screw  8,  which  rests 
upon  the  support  9  screwed  on.  When  the  stock  flows  into  the  hopper 
and  presses  the  gate  3,  the  pressure  is  communicated  to  the  upper  part 
of  the  crank  lever  7,  which  stretching  the  spring  inclines  to  the  left.  With 
the  view  to  give  the  greatest  declination  desired  to  the  gate  there  is  set  a 
screw  20,  with  the  aid  of  which  the  limit  declinations  may  be  adjusted. 
The  connecting  rod  6  in  its  lower  end  has  an  oblong  hole  for  the  pin  of  the 
lever  7.  The  length  of  this  connecting  rod  6  may  be  adjusted  by  means 
of  a  nut  connected  with  the  joint  part  of  the  connecting  rod  and  set  on 
the  screw  part  of  the  coupling  rod.  The  pressure  of  the  levers  7  upon 
the  gate  is  adjusted  by  tightening  the  spring  with  the  screw  to  which  it 
is  joined.  To  open  the  gate  the  axis  4  is  turned  with  a  handle  on  the 
outside  (not  shown  in  the  drawing)  in  the  direction  opposite  to  that  of 

1  French  patent,  No.  429,736,  of  1911. 


FIG.  231. 


CHAP,  iv] 


FLOUR   MILLING 


261 


the  clock  hand.  The  finger  22  lifts  the  axis  24,  together  with  the  gate 
connected  with  this  axis,  by  a  wall  bracket  17.  When  the  axis  4  is  turned 
back,  the  gate  3  drops  under  the  influence  of  its  proper  weight  and  is 
pressed  to  by  the  screw  8,  as  the  connecting  rod  6  turns  the  crank  lever  7 
round  its  axis  in  the  direction  of  the  clock  hands.  Simultaneously  with 
the  closing  of  the  gate  3  the  feeding  rolls  come  to  a  standstill,  which  is 
effected  with  the  aid  of  an  ordinary  appliance  of  cross-head  couplings 
set  in  the  same  manner  as  in  Ganz's  mill. 

Single-roll  Feeding. — The  single-roll  feeding  of  the  factory  of  Thos. 
Robinson  in  Rochdale  is  shown  in  Fig.  232.  The  stock  flows  into  the 
hopper  A  and  presses  with  its  weight  upon  the  gate  23  connected  by  a 
joint  24  with  the  fixed  wall  7  of  the  hopper.  The  pressure  is  transmitted 
through  a  joint-stop  26  to  the  crank  lever  20  set  fast  on  the  axis  13. 


M 


FIG.  232. 

On  the  same  axis  there  are  set,  also  fast,  the  levers  12  with  bearings  11 
for  the  roll  3  (Fig.  232,  //I).  When  the  lever  moves  to  the  right  and 
turns  the  axis  13  the  roll  3  likewise  moves  to  the  right  (arrows)  and  opens 
the  passage  for  the  product  between  itself  and  the  feeding  roll  2.  Though 
the  roll  3  also  rotates,  the  feeding  is  performed  by  the  roll  2,  while  the 
first  one  only  closes  the  passage  of  the  product  conveyed  to  the  rolls  28 
down  the  plate  a.  The  pressure  upon  the  gate  23  is  adjusted  by  the 
spring  21  by  means  of  the  screw  22,  and  the  widest  opening  is  set  by 
the  spring  27.  The  feed-rolls  are  brought  into  motion  in  the  following 
manner  (Fig.  232,  //  and  ///)  ;  the  roll  2  is  revolved  by  a  flexible  gearing 
from  a  pulley  set  on  the  axis  of  the  grinding  roll  and  a  belt-pulley  on  the 
axis  8  of  the  feed-roll  2.  On  the  left-hand  side  (//  and  ///)  of  the 
axis  13  there  is  shown  a  chain  gear  to  the  loose-toothed  wheel  18  on 
the  axis  13.  The  chain  wheel  16  is  made  in  one  piece  with  18.  From 
16  the  rotation  is  transmitted  to  the  roll  3  by  a  chain  wheel  15.  When 
the  axis  13  is  turned  by  a  handle  or  by  the  pressure  of  the  product  upon 


FLOUR   MILLING  [CHAP.  iV 

the  lever  20  through  the  gate  23,  the  chain  wheel  15  rolls  over  the  chain 
wheel  16  but  is  not  disengaged  from  it.     To  prevent  the  dirt  in  the 

product  from  penetrating  into 
the  joints  24  and  those  of  the 
stop  26,  the  ends  of  the  gate  23 
are  covered  over  with  a  leather 
lining  25. 

The  roll  2  is  90  mm.  in 
diameter  and  runs  at  fifty  re- 
volutions per  minute,  while  the 
diameter  of  the  roll  3  is  25  mm. 
and  its  velocity  eight  to  ten 
revolutions. 

A  more  simple  single-roll 
feeding  mechanism,  evolved  also 
by  Thos.  Robinson,  is  shown  on 
Fig.  233.  From  the  hopper  A 
the  stock  flows  on  to  the  roll 
d  and  is  thrown  upon  the 
supplying  plate  c  by  pressing 
off  the  gate  B  rotating  on  the  axis  o.  The  pressure  of  the  gate  is 
adjusted  by  a  spring  E  which  transmits  the  pressure  by  levers  (7,  while 
the  tension  of  the  spring  is  varied  by  a  nut  a  running  on  the  screw  b. 
The  left-hand  end  of  the  screw  is 
joined  by  the  fork  G  screwed  into 
an  arm  on  the  frame  F.  The  de- 
tails are  given  in  the  drawings  / 
and  //.  The  diameter  of  the  roll 
is  100  mm.  and  its  speed  reaches 
up  to  forty  revolutions. 

In  this  mill  the  different  velocities 
of  the  rolls  performing  an  equal 
number  of  revolutions  is  obtained 
owing  to  their  diameters  being 
different.  The  channel  Z  serves  for 
ventilating  the  mill. 

On  Fig.  234  the  single-roll  feeding  of  the  mill  from  G.  Wegmann's 
factory  is  shown.  The  left  half  of  the  mill  is  for  breaking,  the  other  one 
— with  porcelain  rolls — for  the  reduction  of  middlings.  Let  us  examine 
the  feeding  process  in  the  former  section  of  the  mill.  The  stock  flows 


FIG.  234. 


CHAP.    IV] 


FLOUR   MILLING 


253 


into  the  hopper  A,  presses  open  with  its  weight  the  gate  d,  and  is  stirred 
loose  if  it  is  in  lumps  (this  happens  when  the  grain  is  moist)  by  a  paddle 
roll  «]_.  By  turning  the  gate  g,  as  indicated  by  the  arrow,  the  passage 
is  opened  to  the  feed  roll  a  from  which  the  product  runs  to  the  grinding 
rolls.  The  plate  /  isolates  the  product  from  the  space  between  the 
partitions  of  the  mill  and  of  the  bottom  roll,  where  it  might  fall  in  acci- 
dentally. The  number  of  revolutions  of  the  feeding  roll  is  about  sixty, 
and  the  diameter  is  40  to  50  mm. 

The  feeding  of  the  porcelain  rolls  is  similar  to  the  system  of  Thomas 
Robinson's  examined  above.  Both  the  halves  of  the  mill  are  ventilated 
on  the  principle  of  counter  currents  through  the  channel  B. 

American  Feeding  Mechanisms. — Just  as  complicated  as  are  the  feeding 


FIG.  235. 

mechanisms  of  the  European  constructors,  so  simple  are  those  of  the 
Americans.  Very  many  American  factories  prefer  a  type  of  feeding  de- 
vice analogous  to  the  intermittently  shaken  shoe  for  feeding  millstones 
or  a  single-roll  system,  but  in  none  of  the  American  constructions  do 
we  find  a  two-roll  feed.  Further,  in  the  American  feeding  mechan- 
isms, the  plates  supplying  the  stock  to  the  grinding  rolls  are  totally 
absent. 

On  Fig.  235  may  be  seen  both  the  types  of  American  feeding 
mechanisms,  from  the  factory  of  Nordyke  &  Marmon  Co.  On  the  right- 
hand  side  of  the  mill  we  have  two  gates  N  and  M  which  form  the  hopper. 
Influenced  by  the  weight  of  the  product  the  gate  M  turns  round  the 
axis  of  the  fastening  and  the  stock  falls  on  the  gate  N,  which  is  kept 
vibrating  by  cross-heads  k.  The  cross-heads  run  at  the  rate  of  up  to  250 
revolutions  per  minute.  Fig.  236  shows  a  section  in  perspective  of  this 
feeding  mechanism.  Both  the  receiving  and  the  feeding  gates  are 


254 


FLOUK   MILLING 


[CHAP,  iv 


furnished  with  taper  pins  set  in  chess-board  order,  the  purpose  of  which 
is  to  break  up  any  lumps  in  the  product. 

Receiving  a  large  number  of  oscillations,  the  gate  B  loosens  the 
product  well  and  feeds  it  in  an  even  sheet  to  the  grinding  rolls. 

On  Fig.  237  is  shown  a  perspective  section  of  the  roller-feed.     The 


FIG.  236. 


gate  B  is  suspended  on  an  axis  to  the  ends  of  which  on  the  outside  the 
counterweights  C  are  fixed  for  regulating  automatically  the  passage  of 
the  stock  between  B  and  the  feeding  roll. 

Fig.  238  represents  the  feeding  device  of  the  factory  of  AUis-Chalmers 


FIG.  237. 

Co.  in  Milwaukee.  The  stock  runs  into  the  distributing  box  A  divided 
by  an  adjustable  partition  B,  with  the  aid  of  which  the  quantity  of 
product  flowing  into  the  right-  and  the  left-hand  section  of  the  mill 
may  be  regulated. 

The  feeder  C  is  formed  of  a  fixed  plank  h  and  a  gate  a  suspended  on 


CHAP.    IV] 


FLOUR   MILLING 


255 


two  bolts  *  passing  through  holes  in  the  lid  of  the  feeder.  The  clear- 
ances in  the  lid  and  the  ball-washer  e  allow  the  gate  a  to  swing  to  the 
left  under  the  pressure  of  the  product.  The  gate  a  may  be  drawn  up 
with  the  aid  of  the  nuts  g.  The  automatic  adjustment  of  the  flow  is 
performed  by  means  of  fingers  c  and  counterweights  d.  The  largest 
desired  opening  is  set  by  the  stopbolts  k.  For  ventilating  both  the 
pairs  of  rolls  there  is  a  channel  D  wherefrom  the  air  is  exhausted  through 
the  side  holes  E.  The  channel  down  the  full  length  of  the  box  A  is 
covered  over  by  an  iron  lid  F. 

Besides  vibrations  by  cross-heads  some  factories  make  connecting- 
rod  gears.  Fig.  239  illustrates  such  a  feeding  mechanism  from  the 
factory  of  Noye  Manufacturing  Co.  From  the  hopper  A  the  product 
falls  into  the  shoe  B  suspended  on  springs  a  by  an  eccentric  connecting- 
rod  C.  The  flow  is  regulated  by  the  gate  b  with  counterweights  c. 


FIG.  238. 


FIG.  239. 


From  the  shoe  B  the  product  passes  directly  to  the  slowly  rotating 
roll.  The  number  of  vibrations  of  the  shoe  reaches  up  to  200  per  minute. 

The  results  of  feeding  with  an  American  mechanism,  as  was  said 
above,  are  quite  satisfactory.  Still  the  reciprocating  motions  of  the 
working  organs  ought  to  be  avoided,  even  though  the  inertia  of  the 
masses,  as  it  is  in  the  present  case,  be  insignificant. 

Estimation  of  the  Feeding  Mechanisms. — The  types  of  feeding  mechan- 
isms examined  may  be  divided  into  two  principal  groups  :  those  where, 
after  the  feed  rolls,  the  stock  is  passed  to  the  grinding  rolls  down 
a  plate,  we  shall  name  mechanisms  with  compulsory  feeding  ;  while 
those  in  which  the  stock  falls  free  upon  the  working  surfaces  of  the  rolls 
will  be  called  mechanisms  with  free  feeding. 

In  the  beginning  of  the  preceding  chapter,  the  requirements  which 
the  feeding  mechanism  should  satisfy  were  mentioned.  Basing  our 
estimate  of  the  mechanisms  with  compulsory  and  free  feeding  upon  the 
third  and  fourth  requirements,  i.e.  the  shortest  route  from  the  feeding 


256  FLOUR    MILLING  [CHAP,  iv 

mechanism  to  the  rolls  and  absence  of  injurious  resistances  on  the  way 
of  the  stock,  we  must  give  preference  to  the  mechanisms  with  free 
feeding. 

If  we  turn  to  the  constructions  of  compulsory  feeding  we  shall  see 
that  in  the  most  favourable  case  the  supplying  plates  offer  an  inclined 
plane,  and  often  a  rather  long  way  over  a  curved  surface.  In  the  first 
and  in  the  second  case,  this  way  is  longer  than  the  falling  of  the  product 
from  the  feed  roll  straight  upon  the  rolls  (the  line  of  fall  will  lie  in  a 
parabola,  for  the  stock  is  under  the  influence  of  its  weight,  and  is  flung 
off  the  roll  with  the  initial  velocity  at  an  angle  to  the  vertical).  Spending 
more  time  on  its  way  the  product  becomes  heated  to  a  greater  extent 
before  reaching  the  rolls.  But  if  the  ventilation  is  good,  this  circumstance 
is  of  little  consequence.  The  chief  point  is  that  in  travelling  over 
the  plate,  the  product  has  to  overcome  the  power  of  friction,  owing  to 
which  its  velocity,  and  consequently  the  capacity  of  the  mill,  diminishes. 

Another  very  injurious  circumstance  lies  in  the  fact  that  on  the 
plates,  especially  when  a  moist  product  is  being  reduced,  knots  are 
formed  which  break  up  the  solid  sheet  of  stock  into  separate  streams. 
This  disorder  in  feeding  is  particularly  noticeable  if  semolina  and 
middlings  are  the  products  treated. 

The  formation  of  the  streams,  or  the  so-called  paths,  is  brought 
about  in  the  following  manner.  When  different  kinds  of  product, 
besides  the  grain,  run  down  the  plate,  the  soft,  mealy,  glutinous  particles 
stick  to  its  surface.  Around  them  fresh  particles  collect  and  stick  to 
them,  thus  forming  a  knot,  and  the  path  is  ready.  The  stock  running 
in  is  turned  aside  by  those  bunches,  and  the  sheet  of  product  consists 
of  separate  thick  streams.  The  feeding  is  uneven  ;  one  part  of  the  work- 
ing length  of  the  rolls  remains  unused,  while  the  other  is  overloaded  and 
crushes  the  stock  to  flakes.  The  capacity  of  the  mill  decreases. 

The  supporters  of  compulsory  feeding  adduce  in  its  defence  the 
consideration  that,  if  the  process  of  reduction  on  rolls  is  correctly  per- 
formed, the  necessary  movement  and  a  rationally  arranged  ventilation  will 
prevent  the  mealy,  glutinous  particles,  which  cause  the  formation  of  the 
paths,  from  falling  upon  the  feed  rolls. 

However,  these  arguments  are  feeble.  It  should  be  noted  that 
there  is  no  idea  of  supplying  the  grinding  rolls  with  a  product  totally 
free  of  moist,  glutinous  particles,  however  perfectly  the  movement  might 
be  arranged.  When  the  middlings  are  ground  those  particles  are  nearly 
always  present.  The  miller  attending  the  operation  can  easily  obtain 
proofs  of  it.  A  constant  flaking  of  the  meal,  and  an  excessive  heating  of 


CHAP,  iv]  FLOUR   MILLING  257 

the  product  discharged,  very  often  points  to  an  unevenness  in  the  feeding, 
caused  by  the  paths  formed  on  the  plate.  An  inspection  of  the  feeding 
appliance,  and  putting  the  plate  in  order,  is  of  great  assistance  in  the 
process.  This  inspection  should  be  performed  every  four  to  six  hours. 

In  the  breaking  process  the  paths  are  found  more  seldom  ;  the 
rough  break  stock  cuts  the  knots  off  as  soon  as  they  appear. 

The  danger  of  the  mealy  particles  sticking  to  the  plate  and  gathering 
into  knots  is  considerably  alleviated  if  a  perfectly  dry  stock  is  fed  in. 
This  is  attained  by  the  arrangement  of  ventilation,  the  main  purpose  of 
which  in  a  roller  mill  is  to  exhaust  the  warm,  moist  air.  The  fact  must 
be  kept  in  mind,  however,  that  a  perfect  ventilation  in  this  respect 
appears  only  as  a  palliative,  which  impedes  but  does  not  obviate  the 
formation  of  knots  on  the  surface  of  the  plate.  We  must  also  not  forget 
that  so  fine  and  tender  a  product  as  the  fine  middlings  are  to  be  dealt 
with.  The  very  least  obstacle  is  sufficient  to  build  a  path.  The  slightest 
traces  of  moisture  would  suffice  for  the  exceedingly  small  hygroscopic 
particles  of  meal  to  form  a  knot.  But  moisture  is  always  present  even 
with  the  best  of  ventilation. 

The  following  proves  this  statement  to  be  true.  With  a  rational 
ventilation  the  particles  of  meal  reach  the  feed  rolls  in  a  state  of  normal 
moisture,  but  on  their  way  from  the  feed  to  the  grinding  rolls  they  may 
undergo  a  change  in  that  respect.  In  fact,  with  the  passage  of  the 
product,  both  the  product  itself  and  the  working  rolls  become  heated. 
Owing  to  this,  a  part  of  the  moisture  contained  in  the  product  passes 
into  air,  which  will  be  slightly  warmer  than  the  product.  This  air 
enriched  with  moisture,  in  spite  of  a  perfect  ventilation,  will  have  time 
to  return  this  moisture  to  a  cooler  hygroscopic  product — the  gluten  ; 
the  moisture  will  precipitate  upon  the  product.  It  will  be  absorbed  by 
the  finest  hygroscopic  particles  of  the  meal,  rich  in  gluten,  which  will 
settle  in  the  lower  end  of  the  plate.  To  this  we  must  add  that  the  air 
impregnated  with  moisture  settles  immediately  on  the  cold  plate,  which 
facilitates  the  formation  of  paths.  This  latter  remark,  however,  is 
applicable  only  to  the  beginning  of  the  operation,  for  the  plate  also 
becomes  heated  soon.  It  goes  without  saying  that  we  have  in  view 
formations  of  dew  (both  on  the  product  and  on  the  plate)  imper- 
ceptible to  the  eye  and  the  hand,  and  such  formations  are  possible 
even  if  the  mill  is  ventilated,  which  is  proved  by  experiment,  for  the 
plates  of  the  ventilated  mills  have  to  be  cleaned  just  as  those  of  the 
non- ventilated  mills,  though  more  rarely.  The  harmfulness  of  the  use 
of  plates,  even  if  used  with  the  best  modern  ventilation,  is  perceptible. 


258  FLOUR    MILLING  [CHAP,  iv 

In  appraising  the  feeding  mechanisms,  the  accessibility  of  their  parts 
and  operation  for  inspecting  purposes  must  be  considered.  In  this 
respect  the  compulsory  feeding  almost  in  all  makes  is  placed  in  an 
unfavourable  light.  This  defect  in  feeding  is  particularly  notice- 
able on  Fig.  223,  p.  245.  Here  the  product  may  be  seen  through  the 
inspection  window  B  only  at  the  moment  it  leaves  the  feeding-roll  5 
and  partly  when  on  the  plate  r.  The  plate  r  itself  is  quite  inaccessible 
to  inspection,  and  so  far  removed  from  B  that  its  extraction  with  the 
view  to  freeing  it  of  the  knots  is  extremely  difficult.  The  constructors 
upholding  the  compulsory  feeding  ought  to  accept  it  as  a  rule,  that  the 
supplying  plates  should  be  easy  of  access  and  loosely  suspended,  as  this 
will  facilitate  the  removal  of  the  adhering  product  from  them. 

Whatever  be  the  kind  of  feeding,  forced  or  free,  the  stock  must  be 
delivered  to  the  slow  roll ;  it  is  required  by  the  very  idea  of  the  process 
of  reduction,  that  the  slowly  rotating  roll  should  hold  back  the  pro- 
duct. If  the  stock  falls  on  the  fast  roll,  it  will  be  thrown  against 
the  slow  one,  rebound  from  it  again,  and  hinder  the  other  particles 
from  reaching  the  grinding  surfaces,  thus  lowering  the  quality  of  the 
work. 

6.  Types  of  Roller  Mills 
(i.)  Two-roller  Mills 

Having  become  acquainted  with  the  principal  details  of  roller  mills, 
we  can  formulate  the  requirements  which  must  be  satisfied  by  a  ration- 
ally constructed  machine.  Those  requirements  are  as  follows  : 

(1)  An  even  feeding  of  the  grinding  surfaces,  automatic  adjustment 
and  stoppage  of  the  feeding  mechanism. 

(2)  A  tension  brake  for  the  adjustable  roll. 

(3)  The  tramming  of  the  parallelity  of  the  rolls. 

(4)  The  ventilation  of  the  working  chamber  of  the  mill,  for  cooling 
the  product  and  the  working  parts,  and  for  removing  the  meal-dust. 

(5)  The  work  of  the  mill  easy  of  inspection ;  ease  in  the  observation 
of  the  feeding  process  and  in  taking  samples  of  the  grist  while  the  mill 
is  in  operation  without  any  danger  of  mutilation. 

(6)  Removal  of  the  adhering  product  from  the  working  surfaces. 

(7)  Simple  dismantling  of  the  frame  for  removing  the  rolls. 

(8)  Economical  transmission  of  power  to  the  working  organs. 

Let  us  now  examine  the  European  and  American  types  of  mills, 
and  see  how  far  they  satisfy  the  above  requirements. 


CHAP.    IV] 


FLOUR    MILLING 


259 


Mills  of  Amme,  Giesecke,  and  Konegen. — Fig.  240  represents  a  two- 
roller  mill  with  the  lever  for  the  brake,  to  which  we  shall  return  later, 
taken  off.  To  understand  its  construction  better,  let  us  watch  the 
dismantling  and  fitting  up  of  this  mill.  The  frames  of  the  bottom 
adjustable  bearings  b  are  supported  by  timber  blocks  to  shield  them 
from  the  blow  of  the  axles  when  lowered  against  the  frame  of  the  roll. 
Next  with  the  aid  of  ratchet-braces  d  the  lifting  lever  c  connected  with 


FIG.  240. 


FIG.  241. 


the  bushes  of  those  ratchet-braces  by  a  screw  (Fig.  243)  is  lowered. 
This  is  accomplished  by  turning  the  ratchet-braces  d  in  the  direction 
opposite  to  the  movement  of  the  clock  hand.  Further,  the  nuts  and 
lock-nuts  e  are  screwed  off  up  to  the  plugs  /.  Then  the  whole  system 
on  which  the  adjustable  bearings  are  suspended  becomes  free,  and  is 
easily  deflected  by  the  rotation  round  the  axis  of  its  eccentric  fastening, 
as  the  fork-shaped  tail  of  the  bearing  frame  (Fig.  244)  rests  free  on  the 
cup  of  the  brake.  The  lever  c  assumes  the  position  shown  on  Fig.  241, 
after  which  the  upper  part  of  the  frame  is  removed.  On  taking  away 


260 


FLOUR    MILLING 


[CHAP,  iv 


the  timber  blocks  the  adjustable  bearings  are  carefully  lowered,  until 
the  axles  of  the  rolls  are  lying  in  the  cavity  in  the  casing  of  the  frame. 
The  lids  e  of  the  stationary  bearing  and  i  of  the  adjustable  bearing  are 
removed  ;  it  is  then  easy  to  take  out  first  the  upper  then  the  bottom  roll. 
The  construction  of  the  ball-bearings  will  be  examined  below,  while 
for  the  present  we  shall  occupy  our  attention  with  a  four-roller  mill 


l) 


FIG.  242. 

(Fig.  242),  where  the  feeding  mechanism  and  the  brake  may  be  inspected. 
The  feeding  is  performed  in  the  following  manner  :  a  loosely  sus- 
pended gate  w  has  an  adjusting  valve  g,  which  may  be  lowered  and  raised 
by  means  of  screws  k,  increasing  and  reducing  the  passage  of  stock.  By 
the  pressure  of  the  product  the  gate  declines  to  the  right  and  is  retained 
in  the  position  of  the  largest  desired  opening  by  a  stop -screw  e,  with  the 
aid  of  which  the  width  of  that  opening  may  be  altered.  On  the  outside, 
the  gate  w  has  a  counterweight  running  along  the  lever  e,  or,  in  other 


CHAP.   IV] 


FLOUR    MILLING 


261 


makes  of  the  same  factory,  pushed  by  a  spring,  as  in  G.  Luther's  mill 
already  examined.  From  the  fast  feeding  roll  the  stock  flows  down 
the  plate  n  to  the  fast  grinding  roll,  which  passes  it  to  the  plate  o  ;  the 
plate  o  directs  the  stock  to  the  slowly  revolving  bottom  roll.  Both  the 
plates  are  suspended,  and  may  easily  be  removed  through 
the  doors  in  the  hopper  of  the  mills. 

The  adjusting  mechanism  has  the  following  arrangement  : 
the  frame  of  the  adjustable  bearing  has  two  arms  (Fig.  243), 
of  which  the  right-hand  one  with  a  fork-shaped  tail  rests  on 
the  cup  d  with  a  spring,  while  the  left-hand  one  is  set  on  an 
axis  of  rotation  fixed  in  the  frame  of  the  mill.  The  finger  set 
in  the  hub  p  of  the  frame  has  an  end  F  of  a  hexahedral  section 
(Fig.  244).  On  F  there  is  set  an  eccentric  ball  hub  q  fastened 
to  the  collar  of  the  finger  by  a  bolt  5,  the  nut  of  which  is 
covered  by  the  washer  t,  held  by  a-  nut  u.  Between  the 
hubs  p  and  q  there  is  a  washer  v.  Turning  the  nut  s,  after 
having  previously  removed  the  nut  u  and  the  washer  t,  we  turn 
the  hub  q  together  with  the  finger  F,  thus  setting  the  axis  of 
the  adjustable  bearing  in  a  position  parallel  to  the  axis  of 
the  fixed  bearing.  This  fitting  up  is  generally  performed 
accurately  in  the  factory.  A  more  simple  truing  up  is 
performed  with  the  aid  of  a  spring  brake  already  examined.  In 
Fig.  243  is  shown  this  brake  for  porcelain  rolls.  The  same  fork-shaped 
tail  rests  upon  the  cup  d,  in  which  there  is  a  spring  resting  with  its  lower 
end  upon  a  nut  m,  its  tail  entering  into  the  aperture  of  the  cup.  The 

top  end  of  the  brake  rod  is 
set  on  a  finger  eccentrically 
positioned  in  respect  to  the 
axis  of  rotation  of  the  lever 
A  (Fig.  242).  The  raising 
or  lowering  of  the  bearing 


771 


FIG.  243. 


IS 


FIG.  244. 


performed  roughly  by 
turning  the  nut  m,  and 
more  accurately  by  a  ratchet- 
wheel  nut  connecting  the  top 
and  the  bottom  part  of  the  rod.  Over  the  roundly  ground  fork  of  the 
lever  there  is  set  a  washer  with  a  ball-shaped  cavity,  held  by  a  nut  r  and  a 
lock-nut  s.  When  the  pressure  upon  the  rolls  exceeds  the  set  limit,  the  fork 
of  the  tail  presses  upon  the  cup  and,  compressing  the  spring,  drops  down. 
If  the  bearing  is  to  be  lowered  and  the  rolls  put  out  of  gear,  the  lever  d  is 


262  FLOUR   MILLING  [CHAP,  iv 

disengaged  from  the  lever  /,  and  then  the  fork,  pressed  by  the  weight  of 
the  roll,  lowers  the  whole  rod.  A  more  accurate  adjustment  of  the  dis- 
tance is  attained  with  the  aid  of  a  hand- wheel  E  which,  when  turned, 
pushes  forward  the  lever  A  and  lifts  the  front  and  the  back  rods  t,  since 
the  roll  with  eccentric  fingers  is  let  through  the  box  of  the  frame. 

The  motion  is  communicated  to  the  feed  rolls  from  the  fast  grind- 
ing roll  by  belting  to  the  larger  and  by  a  gear  drive  from  the  larger  to  the 
smaller  roll.  The  feeding  rolls  rotate  with  the  ordinary  velocities.  The 
throwing  off  and  in  of  the  feed  rolls  is  performed  by  a  cross-head 
coupling  on  the  axis  of  the  large  roll,  as  in  Ganz's  mill. 

The  rotation  is  transmitted  from  the  fast  to  the  slow  grinding  roll 
also  by  means  of  a  gear  drive.  The  mills  in  question  have  ordinary  ring 
lubricating-  or  ball-bearings. 

The   fitting  of    the  gear-wheels,  belt-pulleys    and    ball-bearings  on 


§-.- 


FIG.  245.  FIG.  246.  FIG.  247. 

these  mills  is  of  some  interest,  and  we  shall  therefore  direct  our  attention 
to  those  details. 

Figs.  245  and  246  illustrate  the  keying  on  of  the  gear-wheels  or  belt- 
pulleys  by  means  of  two  wedge-shaped  keys  b  and  c.  The  chain-wheel 
is  set  on  the  shaft  so  as  to  allow  easy  access  to  the  screw-threaded  holes  a, 
made  for  taking  the  chain-wheels  off.  Then  the  key  b  is  set  in  first,  the 
key  c  laid  on  it,  and  both  are  hammered  in  with  the  calculation  that  the 
end  of  the  key  c  should  protrude  not  more  than  7  to  8  mm.  outside  the 
hub  of  the  gear-wheel.  When  the  pulley  is  to  be  taken  off  the  key  b 
is  knocked  aside  a  little  to  the  left,  which  causes  the  key  c  to  become 
loosened  and  easy  to  extract.  The  gear-wheel  is  taken  off  with  the  aid 
of  a  cross-head  (Fig.  247)  with  bolts  running  freely  through  it  and  screwed 
into  the  holes  a.  The  middle  bolt,  entering  into  the  thread  of  the  cross- 
head,  rests  against  the  centre  of  the  shaft.  In  screwing  the  middle  bolt 
into  the  cross-head,  we  obtain  a  tension  in  the  side  bolts,  which  evenly, 
without  any  crookedness,  draw  off  the  chain-wheel  or  the  belt-pulley. 

The  essential  part  of  the  ball-bearing  is  the  steel  rings  with  balls 
between  them,  of  which  one  is  set  fast  on  the  journal  of  the  shaft,  while 
the  other  one  is  held  in  the  frame  of  the  bearing.  The  rings  with  balls 


CHAP.    IV] 


FLOUR    MILLING 


263 


fitted  in  beforehand  are  warmed  during  a  period  of  about  half  an  hour  in 
machine  oil  of  40°  C.  and  set  on  the  journal  (Fig.  248).  To  bring  them  up 
to  the  collar  of  the  journal  a  free  cast-iron  hub  /  is  set  on  the  journal, 
and  a  piece  of  wood  having  been  placed  under  the  right-hand  end,  it  is 
knocked  with  a  lead  hammer  until  the  hub  pushes  the  rings  to  the  collar. 
For  taking  the  bearings  off  there  is  also  a  cross-head  (Figs.  249  and  250) 
with  bolts  d  and  a  flange  b.  On  the  journal  between  the  bottom  ring  of 
the  bearing  and  the  flange  a  built-up  bush  a  is  placed  so  that  its  section 
lies  on  a  plane  with  the  axes  of  the  bolts  d.  Then  the  bolt  e  resting  against 
the  centre  of  the  journal  is  screwed  into  the  cross-heads,  and  in  this  manner 
tightens  the  rings  with  the  balls  without  damaging  the  journal. 

The  feeding  mechanism  of  the  Amme,  Gieseke,  and  Konegen's  mill'we 
have  examined  has  the  defects  common  to  all  inaccessible  feed  plates. 
In  attempting  to  avoid  these  defects  the  factory  has  evolved  a  new  design 


TT 


FIG.  248. 


Fia.  249. 


FIG.  250. 


for  setting  the  plates,  the  aim  of  which  is  to  curtail  the  route  of  supply 
and  make  the  removal  of  the  knots  from  off  the  feed  plate  more  easy. 
This  construction  was  patented  only  in  the  end  of  1911,  and  has  not  made 
its  appearance  on  the  market  yet.  Here  (Fig.  251)  we  have  already 
only  one  supplying  plate  a  connected  by  a  joint  rod  b  with  the  controlling 
door  c.  '  The  axis  of  rotation  of  the  plate  below  is  a.  Another  plate  is 
set  to  prevent  the  product  from  accidentally  slipping  through  on  to  the 
bottom  roll.  This  position  of  the  plate  a  allows  any  knots  to  be  removed 
without  taking  it  out. 

The  "  Diagonal  "  from  the  works  of  Dobrovy  and  Nabholtz.—As  in  the 
case  of  the  preceding  mill  too,  both  the  halves  of  the  Dobrovy  and 
Nabholtz  mill  operate  quite  independently  of  each  other,  having  only  a 
common  ventilation  chamber  (Fig.  252). 

From  the  hopper  A  the  product  runs  to  the  two  feeding  rolls  aa  : 
the  slowly  rotating  top  roll  passes  the  stock  to  the  fast  bottom  one, 
which  in  its  turn  throws  it  upon  the  nickel-plated  feed  plate  b.  This 


264 


FLOUR   MILLING 


[CHAP,  iv 


plate  delivers  the  product  to  the  grinding  rolls  in  a  tangential  direction. 
The  distance  between  the  feed-hopper  and  the  grinding  surface  of  the  rolls 
has  been  reduced  to  a  minimum,  in  comparison  to  the  preceding  mill. 

The  rolls  are  put  in  gear  by  means  of  a  rod  c  with  a  handle  d,  which 
when  pressed  is  caught  by  the  lever  e.  At  the  same  time  a  system  of 
levers  /  and  g  turns  the  axis  o,  which  with  the  aid  of  the  lever  h  eccen- 
trically set  on  it,  raises  the  bottom  grinding  roll.  The  feeding  device  is 
thrown  in  by  a  lever  c  with  an  inclined  segment  k  acting  upon  the  fork- 
shaped  rod  i. 

The  parallelism  of  the  grinding  rolls  is  set  by  means  of  hand- wheels 
m.  By  turning  the  levers  q  with  the  screws  r,  the  gate  t  may  be  set  in 
any  position,  in  which  it  will  be  retained  by  the  springs  s. 

The  automatic  throwing  out  of  the  rolls 
and  the  stoppage  of  the  feed  are  effected 
by  the  action  of  the  weight  g  upon  the 
levers  c  and  p  in  a  manner  already  known. 

The  grinding  rolls  are  aspirated  in  the 
direction  indicated  by  the  arrows  1,  3,  and  4 
in  the  drawing,  and  the  air  on  entering  the 
chamber  of  the  mill  through  the  fissures 
under  the  lid  exhausts  the  grinding  rolls  from 
below  and  then  passes  up. 

The  bearings  of  the  rolls  are  made  of 
phosphor-bronze  and  furnished  with  ring 
lubrication. 

The  gear-wheels  for  transmitting  the 
motion  to  the  rolls  with  double  helical- like  teeth  are  set  in  special  cases 
serving  them  as  oil  boxes. 

The  slow  feed  roll  is  turned  by  a  belt-drive  from  the  belt-pulley  on 
the  axis  of  the  fast  grinding  roll,  and  from  the  slow  feeding  r6ll  to  the 
fast  by  toothed  gearing.  The  built  cross-head  coupling  is  set  on  the  axis 
of  the  slow  feeding  roll. 

French  Roller  Mill. — On  Fig.  253  may  be  seen  the  mill  of  one  of  the 
largest  French  milling  machinery  works,  Teisset,  Chapron  &  Brault 
Freres,  in  Paris  and  Chartres. 

The  section  illustrates  the  position  of  the  feeding  mechanism  and 
grinding  rolls,  showing  the  fast  grinding  roll  with  fixed  bearings  to  be  at 
the  top,  and  the  slow  roll  with  the  brake  below.  The  incline  of  the  plane 
of  the  axes  forms  an  angle  of  50°  with  the  horizontal  plane. 

The  feeding  is  performed  by  two  rolls  a  and  b  with  corresponding 


FIG.  251. 


CHAP,  iv] 


FLOUR   MILLING 


265 


differential  velocities  and  an  adjustable  gate  c  discharged  by  means 
of  a  spring  set  on  the  outside  of  the  mill.  The  stream  of  product 
observed  through  the  glass  door  d  in  the  upper  part  of  the  frame 
glides  down  two  inclined  plates.  From  those  plates  the  stock  falls 
upon  the  slow  grinding  roll  A,  which  carries  it  to  the  fast  roll  B. 


FIG.  252. 

On  opening  the  door  D  in  the  mill,  the  delivery  of  the  milled 
product  may  be  watched  and  samples  obtained  without  any 
difficulty. 

From  the  feeding  rolls  and  on  leaving  the  grinding  roite  the  product 
may  be  taken  by  hand  without  fear  of  any  danger. 

The  exhaust  air  enters  through  the  top  part  of  the  hopper,  follows 


266 


FLOUR    MILLING 


[CHAP.  IV 


the  stock  all  along  its  route,  and  is  exhausted  by  the  aspirator  after  the 
stock  passes  through  the  grinding  rolls. 

The  cast-iron  frame,  judging  by  the  outward  appearance  of  its  con- 
struction, is  rigid,  and  vibration  apparently  obviated.  The  frame  is  lined 
with  timber  on  the  inside  to  prevent  the  walls  from  becoming  cooled,  in 
which  case  the  moisture  is  deposited  and  settles  on  them  and  the  meal 
turns  to  a  paste. 

The  adjustment  of  the  grinding  rolls  here,  as  in  other  types  of  mills 
too,  consists  of  two  separate  processes  :  (1)  tramming  the  adjustable 


FIG.  253. 

roll  in  respect  to  the  fixed  one,  and  (2)  setting  the  adjustable  roll 
nearer  to  or  farther  from  the  fixed. 

The  tramming  in  respect  to  the  fixed  roll  in  every  bearing  is  performed 
by  means  of  a  hand-wheel  G  resting  upon  a  spring  encased  in  a  box  H . 

The  brake-mechanism,  as  well  as  the  automatic  stoppage  of  the  feed, 
in  construction  is  similar  to  those  of  Seek,  with  the  sole  difference 
that  the  brake  is  fitted  to  the  bottom  roll,  while  in  Seck's  mill  it  is 
applied  to  the  top  roll. 

G.  Daverio's  Mill. — The  Swiss  works  of  G.  Daverio  (Zurich)  was  the 
first  to  adapt  the  vertical  position  of  rolls  and  very  soon  began  to  set 
them  diagonally,  convinced  by  experience  of  the  inconvenience  of  the 
plates  supplying  the  stock  to  rolls  so  positioned.  Simultaneously  with 


CHAP,  iv]  FLOUR   MILLING  267 

the  English  works  of  Turner,  Daverio  patented  mills  with  a  diagonal 
disposition  of  rolls,  in  which  the  operation  of  the  feed  plates  is  placed 
in  more  favourable  circumstances.  At  last,  for  the  first  time  in  Europe, 
the  Daverio  works  launched  on  the  market  in  1908  a  model  of  a  mill 
without  any  feed  plates,  and  this  was  soon  imitated  by  other  works. 

Fig.  254  shows  a  Daverio  mill  of  the  latest  model.  The  grain  runs 
into  the  hopper  and  with  its  weight  presses  open  the  feed  gate  adjusted 
by  a  counterweight  b.  The  utmost  opening  of  the  feed  gate  is  set  by 


FIG.  254. 

means  of  a  screw  c.  The  adjustment  of  the  feed  gate  by  hand  is  per- 
formed with  the  lever  d  set  on  the  axis  r  of  the  flap.  The  slowly  rotating 
top  feed  roll  carries  the  stock  to  the  fast  roll,  which  throws  it  directly  on 
the  slow  grinding  roll.  Under  the  frames  there  is  placed  a  plate,  the  duty 
of  which  is  to  collect  the  heavy  extraneous  matter. 

The  tension  brake  in  general  is  the  same  as  in  other  mills,  with  this 
difference  only,  that  the  cup  with  the  spring  forms  one  single  piece  with 
the  tail  I  of  the  adjustable  bearing.  With  the  aid  of  the  lever  a,  connected 
by  an  ordinary  distance  eccentric  with  the  tail  I  of  the  adjustable 
bearing,  the  grinding  rolls  may  be  either  thrown  out  of  gear  or  thrown 
in  for  ordinary  work.  In  throwing  out  the  bottom  roll  the  lever  a 


268  FLOUR   MILLING  [CHAP,  iv 

at  the  same  time  turns  a  horizontal  crooked  lever  round  its  axis,  which 
by  means  of  a  cross-head  coupling  throws  the  rapidly  rotating  bottom 
feeding  roll  out  of  motion.  The  spring  of  the  brake  is  adjusted  by  means 
of  nuts  hf-li.  An  accurate  tramming  of  the  axes  of  the  grinding  rolls  is 
performed  with  a  hand-wheel  g.  The  dismantling  of  the  frame  and  ex- 
traction of  the  grinding  rolls  is  performed  in  the  following  manner.  The 
removable  parts  o  on  either  side,  of  the  frame  are  taken  off.  Then  the 
cotters  i  are  taken  out  and  the  nut  k  loosened,  which  allows  the  cup  m 
to  be  lifted  off,  when  the  lids  of  the  bearings  are  removed  and  the  grind- 
ing rolls  may  be  lifted  out. 

The  ventilating  air  enters  through  the  holes  in  the  lid  of  the  hopper 
covered  over  with  a  dense  sieve,  exhausts  the  rolls  from  below,  and  escapes 
through  the  side  openings. 

The  transmission  of  motion  from  the  fast  top  roll  to  the  bottom  one 
is  done  by  means  of  toothed  wheels  enclosed  in  cast-iron  casings  filled 
with  oil  through  the  inlet  q  up  to  the  level  p. 


(ii.)  American  Roller  Mills 

Not  only  in  Russian  literature  but  in  Western  Europe  as  well  a  total 
absence  of  descriptions  of  American  milling  machinery  in  general,  re- 
specting roller  mills,  is  observable.  Even  so  eminent  an  author  as  Pro- 
fessor Kick  speaks  only  of  Howes'  scouring  machine.  This  circumstance 
is  all  the  more  striking,  since  the  first  teachers  of  the  European  automatic 
milling  engineers  were  Americans.  One  could  learn  a  good  deal  from  them 
even  now.  However,  not  only  in  monographs  and  lectures,  but  even  in 
the  periodical  literature  of  Europe,  we  find  no  material  dealing  with  the 
American  construction  of  milling  machinery.  Is  this  the  usual  conser- 
vatism of  Europe,  or  the  patriotism  of  the  Old  World  ?  We  cannot  under- 
take to  judge,  but  the  fact  is,  that  the  European  constructors  have  been 
deprived  of  rich  material  in  the  possession  of  their  transatlantic  colleagues. 

The  American  roller  mills  are  so  different  and  original  in  their  con- 
structive ideas,  and  besides  that  so  little  known  to  us,  that  we  have  deemed 
it  expedient  to  dedicate  a  whole  chapter  to  their  description. 

We  are  already  acquainted  with  the  feeding  devices  of  the  American 
mills,  and  shall  now  examine  the  brakes  and  the  mill  in  their  full  outfit. 

Fig.  255  represents  J.  Stevens'  two-roller  mill  with  a  brake  of  direct 
action.  The  bearings  a  are  fixed,  the  adjustable  ones  a±  run  in  the  parallel 
guides  of  the  frame.  The  brake  has  the  following  arrangement.  The 
screw  F  freely  passes  through  the  screw  1-2,  entering  the  box  of  the 


CHAP.   IV] 


FLOUR    MILLING 


269 


bearing  and  its  end  protruding  out  of  it.  The  screw  1-2  is  screwed  into 
the  arm  G  of  the  frame.  On  this  screw  a  spring  is  set  which  presses  upon 
the  bearing.  The  grinding  rolls  are  thrown  apart  by  pressing  the  lever  D 
down  with  the  handle  d,  when  the  cross-heads  C  (on  Fig.  1,  with  another 
curve  of  the  lever  D,  it  is  more  clearly  seen)  press  upon  the  protruding 
parts  of  the  screw  F  and  draw  the  bearings  and  the  grinding  roll  with 
them,  to  the  left.  When  the  lever  is  turned  back,  the  spring  brings  the 
bearings  to  their  former  position.  The  distance  of  the  working  surfaces 
is  defined  by  the  size  of  the  protruding  ends  of  the  screws  F.  The 
parallelity  of  the  axes  of  the  rolls  in  a  horizontal  plane  is  set  by  those 
same  screws  being  deeper  or  less  screwed  into  the  frame  of  the  bearing. 


FIG.  255. 

The  head  3  of  the  screw  1-2  serves  for  screwing  it  into  the  arm  of  the 
frame,  and  thus  adjusting  the  distance  to  which  the  bearings  are  removed  ; 
the  nut  4  regulates  the  tension  of  the  spring.  The  motion  is  transmitted 
to  the  roll  by  belt-gearing,  and  the  receiving  belt-pulley  is  on  the  journal 
H  of  the  fast  grinding  roll,  which  transmits  the  motion  to  the  slow  roll 
by  means  of  jockey -pulleys  1^-1  and  II~IIl ;  from  the  shaft  of  the  slow 
roll  a  cross  drive  Ill-Ill \  runs  to  the  feeding  roll.  The  tension  of  the 
belts  is  adjusted  by  a  screw  B  with  a  spring  to  mitigate  the  shocks.  This 
spring  presses  upon  the  adjustable  bearing  of  the  jockey-pulley  /-//,  while 
the  degree  of  its  pressure  is  regulated  by  a  nut  and  a  lock-nut  L 

The  defects  of  the  brake  of  direct  action  were  noted  when  examin- 
ing Noye's  brake.  But  those  mills  do  good  service  in  the  rough  fodder- 
grinding  of  maize,  barley,  oats,  &c.  Among  the  reparable  defects  of 


270 


FLOUR    MILLING 


[CHAP,  iv 


this  mill  we  may  place  the  transmission  of  motion  to  the  feeding  roll 
from  the  adjustable  grinding  roll,  for  when  the  grinding  rolls  are  being 
drawn  apart  the  belt  becomes  stretched  and  then  begins  to  work  badly. 

It  is  to  be  remarked  here  that  the  belting  transmission  of  motion  to 
the  grinding  rolls  is  a  peculiarity  characteristic  of  American  roller  mills. 
Only  in  mills  doing  rough,  coarse  work  do  the  Americans  employ  toothed 
gearing. 

T.  W.  Graham's  original  brake  is  shown  on  Fig.  256.  The  adjustable 
grinding  roll  E  is  set  in  a  bearing  F,  one  tail  of  which  is  connected  with 
the  rod  D,  while  the  other,  G,  with  its  point  H  turned  to  a  globe,  enters  into 

a  cylindrical  socket  in  the  frame  of 
the  fixed  bearing  A,  which  forms  a 
part  of  the  roller  frame.  Through 
the  arm  K  of  the  lower  tail  there 
passes  a  rod  L  to  the  spring  M . 
The  rod  P  eccentrically  set  with 
its  clip  X  on  the  finger  n,  the 
screw  D,  and  the  spring  hold  the 
bearings  in  a  settled  position.  By 
turning  the  handle  N  down  and 
pushing  the  rod  P  likewise  down, 
the  bearing  F  is  made  to  revolve 
round  the  horizontal  axis  of  the 
apple  Q.  To  allow  a  free  lowering 
of  the  left  end  of  the  spring  rod 
Z  there  is  a  clearance  I  in  the 
FIG.  256.  frame.  A  rough  tramming  of  the 

roll-axes  is  done  by  means  of  nuts 

o  and  olt  a  more  accurate  setting  by  the  screw  D  which  also  regulates  the 
working  distance.  The  pressure  of  the  spring  is  adjusted  by  a  nut  12. 

The  brake  of  J.  Dawson's  four-roller  mill  is  given  in  Fig.  257.  The 
lower  tails  D  of  the  adjustable  bearings  E  are  freely  set  on  the  hubs  G 
with  levers  K.  These  hubs  are  eccentrically  fitted  on  the  journals  of 
the  shaft  H,  the  rotatory  motion  of  which  is  stopped  by  bolts  L.  The  top 
tails  of  the  bearings  rest  on  the  spring  V.  The  screw  rods  N  are  fitted 
with  their  slips  on  the  fingers  of  the  discs  R,  one  of  which  has  a  handle  X 
with  a  lock  7.  The  discs  are  fixed  on  the  journals  El  of  the  shaft  E1  with 
keys.  By  turning  the  handle  X  to  the  right  or  left  one  can  bring  the 
grinding  rolls  to  a  fast  or  a  loose  run.  The  tension  of  the  spring  is  ad- 
justed by  a  nut  W  (having  a  washer  on  the  rod  with  a  clearance  behind 


CHAP.    IV] 


FLOUR    MILLING 


271 


it).  Seeing  that  the  hub  G  is  an  eccentric,  by  turning  the  levers  K,  having 
previously  loosened  the  bolts  L,  one  may  set  the  axis  of  the  roll  in  a  hori- 
zontal plane  ;  the  parallelity  of  the  axes  of  the  grinding  rolls  is  established 
by  turning  the  hand- wheels  U  to  the  right  or  to  the  left,  depending  on 
the  direction  in  which  the  axis  slants. 

Special  attention  is  due  to  the  idea  of  adjusting  the  axis  of  the  grind- 
ing roller  in  two  planes — vertical  (by  means  of  an  eccentric  hub  G)  and 
horizontal,  so  simply  brought  into  execution.  We  must  remark  that 
all  European  factories  do  not  give  consideration  to  this  question. 

Fig.  258  shows  us  the  brake  of  a  two-roller  mill,  constructed  by  W.  D. 
Gray,  an  eminent  American  engineer  (Allis-Chalmers  Co.  works).  Here 
both  the  bearings  D  and  D1  are  adjustable  ;  their  axes  of  rotation  are 


,  FIG.  257. 

o  and  ov  The  section  of  the  brake  is  illustrated  on  Fig.  260,  which 
shows  the  rod  E  to  be  an  eccentric  coupling  with  the  axis  bQ  of  the  lever  H . 
The  second  end  of  the  rod  passes  through  the  cup  d  with  a  spring  d±  of 
the  tail  of  the  bearing  D  resting  against  the  screw  d3  with  a  hand-wheel. 
On  the  same  axis  66  there  is  eccentrically  set  the  tail  of  the  bearing  Dlf 
The  grinding  rolls  are  thrown  apart  by  pulling  the  rod  /  to  the  right. 
The  friction  drive  to  the  feeding  roll  is  arranged  as  follows  :  on  the  rod  E 
there  is  a  coupling  Q  with  an  offshoot  q  to  which  the  loose  belt-pulley  M 
is  screwed  by  the  bracket  of  its  hub. 

The  coupling  Q  may  be  moved  up  and  down  the  rod  and  fastened 
with  a  bolt  a.  When  the  rolls  are  set  for  a  working  run,  the  belt-pulley 
M  comes  into  contact  with  the  belt-pulley  N  on  the  journal  of  the  right- 
hand  roll,  and  the  belt-pulley  L  on  the  journal  of  the  feeding  roll. 

Fig.  259  illustrates  the  brake  of  a  four-roller  mill.     The  bearings  of 


272 


FLOUR   MILLING  [CHAP,  iv 

The  details  need  no  explanation,  being  a 


the  middle  rolls  here  are  fixed, 
repetition  of  those  preceding. 

A  more  simple  friction  drive  to  the  feeding  rolls  is  to  be  seen  on 
Pig.  261.  Here  only  one  friction  roll  E  is  loose  ;  to  the  second  feeding 
roll  the  motion  is  transmitted  by  a  crossed  belt.  The  defects  of  the 
friction  drive,  in  the  first  case  (Figs.  258  and  259)  lying  in  the  fact  that 


FIG.  258. 


FIG.  259. 


with  the  change  in  the  working  distance  of  the  grinding  rolls  the  position 
of  the  friction  roll  has  likewise  to  be  altered,  are  removed  here  since  the 
position  of  the  friction  drive  is  independent  of  the  position  of  the  brake 
rod. 

In  Fig.  262  we  see  a  very  ingenious  device  for  stopping  the  operation 
of  the  feed  rolls  by  means  of  an  ordinary  cross-head  coupling  and  a 
loose  belt-pulley  on  the  axis  of  the  feeding  roll.  On  the  left-hand  end 


FIG.  261. 

(top  left-hand  drawing)  of  the  roll  0  communicating  the  motion  to  the  rods 
E  of  the  brakes,  there  is  set  fast  a  hub  p  with  a  screw  arm  P  (Figs.  3  and 
4)  which  catches  the  flange  a  of  the  hub  of  the  belt-pulley  L,  on  the  axis  of 
the  feeding  roll  J.  This  hub  on  its  left-hand  side  is  a  cross-head  coupling 
cogging  in  with  the  hub  of  the  loose  belt-pulley  N.  When  the  rolls  are 
in  a  working  position  the  roll  G  is  turned  so  that  the  screw  flange  of  the 
hub  p  points  downwards  and  the  spring  /  pushes  the  belt-pulley  L  for- 
ward till  it  couples  with  the  belt-pulley  N.  When  the  grinding  rolls  are 


CHAP.    IV] 


FLOUR   MILLING 


273 


running  empty  the  flange  P  disengages  the  belt-pulleys  L  and  N,  and  the 
operation  of  the  feed  rolls  is  discontinued. 

A  similar  device  for   a  loose   and  fast   run   of   the   feed  rolls  with 
toothed   couplings   and  friction  2  is  illustrated  in  Fig.   263,  with  this 


FIG.  262. 


difference  only,  the  disengaging  mechanism  of  the  grinding  roll  connected 
to  brake  hand- wheel,  and  the  connecting  of  the  couplings  or  of  -the 
friction,  is  performed  not  by  a  spring  but  by  a  crank  Lever  R  (with 
or  without  a  fork  at  the  end).  On  the  rod  H,  which  brings  the 


FIG.  263. 

adjustments  into  action,  there  are  two  slides  made  to  fit  the  free  end 
of  the  crank  lever  R.  When  the  rolls  are  in  gear,  and  the  rod  H 
is  pushed  to  the  right,  the  end  of  the  lever  R  falls  into  the  slide  a 
and  keeps  the  coupling  Q  engaged  with  the  hub  of  the  belt-pulley  N  ; 
when  the  run  is  loose,  it  is  held  by  the  slide  a, 


274 


FLOUR    MILLING 


[CHAP,  iv 


The  latest  model  of  W.  D.  Gray's  roller  mill  is  represented  in  Figs.  264, 
265,  and  266.  A  characteristic  peculiarity  of  the  American  roller  mills 
is,  as  has  already  been  mentioned,  the  total  absence  of  toothed  gearings. 
Let  us  note  first  how  the  motion  is  communicated  to  the  rolls.  From 
the  pulley  of  the  transmission  shaft,  the  belt  runs  first  (Fig.  264)  over 
the  belt-pulley  A  of  the  outermost  fast  grinding  roll  and  then  over  the 
jockey-pulley  C  to  B,  the  belt-pulley  of  the  third  on  the  left-hand  side 


FIG.  264. 

fast  grinding  roll.  In  this  manner,  the  fast  rolls  of  the  American  roller 
mills  are  disposed  asymmetrically — the  inevitable  result  of  transmission 
by  belting.  This  arrangement  cannot  be  avoided  if  the  machine  is 
to  be  compact.  The  slow  grinding  rolls  with  belt-pulleys  D  and  E, 
the  second  and  the  fourth,  receive  their  motion  (Fig.  265)  from  the 
belt-pulleys  F  and  G  placed  on  the  same  shaft  as  the  belt-pulley  C. 
The  belt-pulley  C  has  a  double  function  :  firstly,  it  affords  the  possi- 
bility of  enlarging  the  gripping  angle  of  the  belt-gearing  of  the  pulleys  A 
and  B,  secondly,  by  rising  or  falling  it  adjusts  the  tension  of  the  belt, 


CHAP.    IV 


FLOUR    MILLING 


275 


An  adjustment  of  this  kind  of  the  tension  of  belts  is  a  feature  of  the 
construction  of  roller  mills  of  all  American  works,  and  is  of  very  great 
importance.  First  of  all,  the  tension  of  the  belts  being  regulated  in  the 
manner  described  above,  there  is  no  need  to  take  up  the  stretched 
belt ;  but  the  main  point  is  that  by  increasing  the  tension,  we  can  within 
a  limit  of  10  to  20  per  cent,  increase  the  capacity  of  the  mill,  which 
has  often  to  be  done  when  the  mills  are  overloaded.  The  raising 
and  the  lowering  of  the  jockey  pulleys  (7,  F  and  G  is  performed  by  means 


FIG.  265. 

of  hand- wheels  j  and  screw  rods  connected  by  joints  with  the  tails 
of  the  bearings  L,  which  turn  round  the  axis  0.  The  screw  rods  pass 
through  a  consolidated  bracket  Q  with  a  screw  thread.  Before  proceed- 
ing any  further,  we  must  point  out  a  material  defect  in  Gray's  adjustment 
of  tension.  The  planting  of  independent  adjustable  bearings  for  the 
belt-pulleys  C  and  F-G  does  not  exclude  the  possibility  of  the  shaft 
getting  out  of  line,  since  its  horizontality  cannot  be  trued  up  on  the  belt- 
pulleys  F  and  G ;  this  tends  to  make  the  bearing  L  work  hot  and  wear 
irregularly. 

Proceeding  now  to  describe  the  mill,  we  must  point  out  that  the 


276 


FLOUR    MILLING 


[CHAP,  iv 

mechanism  adjusting  the  distance  here  is  improved  in  so  far  that  the 
eccentric  rods  E  of  the  brake  have  one  common  axis  S,  which  simplifies 
the  construction.  On  the  same  axis  is  set  the  tail  of  the  hub  of  the  loose 
belt-pulley,  over  which  there  runs  a  belt  transmitting  the  motion  from 
the  slow  roll  to  the  feeding  rolls.  In  throwing  apart  the  outer  grinding 
rolls  by  turning  the  lever  P  to  the  left  this  loose  belt-pulley  is  dropped 
down,  the  belt  slackens,  and  the  feeding  rolls  stop  operating.  This  belt- 


FIG.  266. 

pulley,  similarly  to  the  guide  belt-pulleys  and  the  belt-pulleys  on  the 
axes  of  the  feed  rolls,  has  collars  (Fig.  266)  which  prevent  the  belt 
from  running  off.  When  the  tension  of  the  belt  to  the  pulleys  of  the 
feed  rolls  is  to  be  increased  the  bolt  holding  the  hub  of  the  tail  of  the 
loose  belt-pulley  is  dropped,  the  tail  turned  to  the  right,  and  the  bolt  is 
again  fastened. 

Nordyke  &  Mormon  Co.'s  Mill. — On  Figs.  267,  268,  and  269  we  see 
the  construction  of  a  roller  mill  of  one  of  the  largest  American  works — that 


,  iv]  FLOUR   MILLING  277 

of  Nordyke  &  Marmon  Co.  at  Indianapolis.     Fig.   267  illustrates  the 


FIG.  267. 


general  view  of  the  mill  (1),  and  the  plan  (2)  with  the  hopper  off,  Fig.  268 
two  sections,  longitudinal  (3),  and  along  the  brake  mechanism  (4),  Fig.  269 


FLOUR   MILLING 


[CHAP.  iV 


details  of  the  drive  to  the  brake  mechanism  and  to  the  feeding  apparatus 
(5,  6,  7,  8,  9,  10,  11).  The  mill  is  driven  by  the  belt-pulleys  1,  2,  3,  4— 
1  and  3  by  means  of  the  belt  12  running  from  the  belt-pulleys  on  the 
shafting,  2  and  4  by  means  of  separate  belts  13  and  14  on  the  belt- 
pulleys  6  and  7.  The  jockey-pulleys  5,  6  and  7  run  through  the  frame 
of  the  mill. 

The  adjustable  bearings  are  built  in  the  following  manner  :  the  two- 
tailed  boxes  D  for  the  bearings  E  below  (Fig.  268,  4)  have  an  axis  of  rota- 
tion d  (a  bolt  screwed  into  the  frame)  on  which  they  are  set  with  their 
eccentric  dt.  This  eccentric  determines  the  distance  to  which  the  adjust- 


FIG.  268. 

able  grinding  roll  springs  open  in  case  a  nail  or  any  other  piece  of 
metal  falls  in  between  the  rolls.  The  bearings  E  have  surfaces  e  and  ez 
turned  in  to  the  corresponding  surfaces  of  the  boxes  D,  to  which  the 
frame  of  the  bearings  is  attached  by  bolts  ev  If  the  axes  of  the 
rolls  require  adjusting  vertically,  the  bolts  e±  are  loosened  and  the 
wedges  e3  tightened.  When  the  regulation  is  ended,  the  bolts  el  are 
readjusted. 

The  rods  F  of  the  brake  pass  through  the  lower  ends  of  the  shoulders 
D,  under  their  joints,  having  the  spring  Fl  on  one  side,  and  the  regulat- 
ing brake  of  the  spring  hand- wheel  F*  on  the  other.  These  hand- wheels 
are  screwed  up  till  the  shoulders  have  a  tension  sufficient  to  com- 


CHAP.   IV] 


FLOUR   MILLING 


279 


municate  a  pressure  of  the  desired  force  to  the  rolls.     When  a  hard  body 
falls  in  between  the  rolls  and  presses  them  apart,  the  springs  contract, 


FIG.  269. 


for  .the  shoulders,  owing  to  the  eccentric  couplings  on  the  bolts,  may 
travel  along  the  axis  d. 

The  rods  G  serve  to  move  the  upper  ends  of  the  shoulders  D  to  the 
right  and  to  the  left,  owing  to  which  the  grinding  rolls  approach  or 


2SO  FLOUR   MILLING  [CHAP,  iv 

separate,  i.e.  the  throwing  in  or  apart  takes  place.  At  its  inner  end 
every  one  of  those  rods  is  connected  by  a  joint  g  with  a  lever  H,  which 
draws  the  shank  with  it  when  moving. 

The  levers  H  have  in  the  frame  A1  axes  of  rotation  d     by  turning  the 
cross-heads  j  the  throwing  in  and  out  of  the  rolls  is  performed. 

The  handles  J1  are  set  on  the  journals  of  the  cross-heads  J.  Those 
handles  have  segments  of  toothed  wheels  J2  at  their  lower  ends.  One  of 
the  toothed  segments  may  be  thrown  off  and  act  independently  of  its 
lever,  if  it  be  desired  that  only  one  side  of  the  mill  should  be  at  work. 
This  is  effected  by  making  the  toothed  wheel  and  the  lever  in  two  parts, 
as  shown  in  Fig.  269  (6  and  11),  with  a  slot  for  the  bolt  i1.  When  it  is 
desired  to  fasten  both  parts  together,  the  bolt  il  is  brought  down,  as 
shown,  to  the  lower  part  of  the  slot  and  fastened  there,  so  that  the  levers 
and  the  segments  form  one  whole  body  and  operate  together.  If  it  is  in- 
tended that  only  one  half  of  the  machine  should  work,  the  bolt  il  is  pushed 
up  to  the  top  part  of  the  slot,  and  then  the  handle  and  the  segment  are 
independent  of  each  other.  As  this  segment  does  not  sit  firmly  on  the  shaft, 
the  opposite  lever  may  be  displaced  without  touching  the  shaft  it  is  set  on. 
With  the  aid  of  the  above  described  adjustment  both  pairs  of  rolls,  or 
either  pair  singly,  can  be  thrown  apart  and  then  again  brought  together 
to  exactly  the  same  distance. 

The  lower  ends  of  levers  j1  are  provided  with  pins  i2,  which,  during  the 
motion  of  the  levers  backwards  and  forwards,  catch  the  claws  11  of  the 
rods  L  (Fig.  269,  7),  which  are  consequently  brought  into  motion  and  draw 
the  shoulders  Kl  and  the  shafts  K  of  the  regulating  gate  by  means  of 
levers  Kl  and  pins  Zx  with  them.  It  is  quite  clear  that  when  the  levers  j 
are  disconnected  and  are  working  independently  of  each  other,  they 
bring  into  action  each  one  of  the  rods  independently. 

The  feed  plates  J  are  of  thin  metal  and  run  along  the  feeding 
rolls  J1  with  claws  j  and  j1  at  the  top.  One  of  these  claws  j  on  each 
one  of  the  plates  couples  with  claw  k  of  the  corresponding  axle  K 
(see  Figs.  8  and  9),  and  in  this  way  the  gate  rises  and  falls  with  the 
revolution  of  the  axle.  Other  claws,  j1,  are  fitted,  so  as  to  be  able  to  catch 
the  stop  screws  j2,  and  consequently  the  gate  is  allowed  to  rise  only  to  a 
certain  height.  It  is  best  for  the  regulating  screws  to  do  the  service  of 
stop  claws  (see  the  fig.) ;  in  that  case  the  rise  and  fall  of  the  feed  gate  is 
under  control.  The  feeding  rolls  J1  are  brought  into  motion  in  the  direc- 
tion pointed  by  the  arrow  by  means  of  belts,  the  distribution  of  which 
in  the  machine  is  marked  in  dotted  lines  on  the  right-hand  side  of  the  plan 
of  the  roller  mill  (Fig.  267). 


.  iv]  FLOUR   MILLING  281 

The  shaft  M  through  a  connecting  gearing  of  the  pulleys  5,  6,  and  7 
is  set  on  bearings  N.  With  the  rising  and  falling  of  that  shaft  the  driving 
belts  12,  13  and  14  are  tightened  and  loosened. 

The  bearings  N  are  set  on  hatchet  stakes  n  fixed  in  the  arms  of  the 
bearings  and  pass  through  guides  a3  and  a4  of  frame  A. 

The  stems  are  connected  by  joints  with  the  upper  parts  of  the  frame  n, 
ending  in  toothed  racks  at  the  top. 

The  toothed  wheels  P  are  set  on  axles  P1  and  engaged  with  the  toothed 
racks  of  the  stems  0,  which  are  thus  enabled  to  rise  and  fall,  dragging  the 
shaft  M  and  the  belt-pulleys  with  them. 

The  motion  is  transmitted  in  the  following  manner  :  the  main  belt  12 
drives  the  pulleys  1,  3  and  5,  turning  the  grinding  rolls  Cl  and  <73  in  one 
direction  and  the  shaft  M  in  another.  With  the  aid  of  belt-pulleys  6 
and  7,  and  belts  13  and  14  running  to  the  belt-pulleys  2  and  4,  the  shaft  M 
turns  the  grinding  rolls  C2  and  <74  in  the  direction  opposite  to  that  of  the 
rolls  Cl  and  O3.  There  is  a  small  pulley  8  on  the  shaft  of  the  roll  C2,  which 
drives  the  pulley  9  by  means  of  a  belt,  one  of  the  feed  rolls  J1,  and 
pulley  10  set  on  the  same  shaft.  The  pulleys  10  and  11  are  connected 
by  a  belt  which  drives  the  other  feed  roll.  The  belts  connecting  the 
pulleys  8  and  9,  10  and  11  are  not  shown  in  the  drawing,  but  their  arrange- 
ment is  marked  by  dotted  lines  on  (2)  Fig.  267. 

On  the  axles  K,  the  closer  to  the  centre  the  better,  there  are  claws 
KI  (6)  coupling  with  the  claws  j  on  the  brushes  and  thus  capable  of 
raising  and  lowering  the  gates,  according  to  the  direction  in  which  the 
rolls  are  turning.  On  these  rolls  (5)  there  are  levers  K1  which  with  their 
weight  turn  the  shafts  in  one  direction  ;  in  the  other  direction  they  are 
turned  by  means  of  claws  I1 11  on  blocks  L,  which  in  moving  lift  the 
shoulders  K1  when  they  come  in  contact  with  those  claws. 

By  means  of  the  rods  L  the  rolls  K  turn  in  one  direction,  covering 
the  plates.  When  it  is  desired  to  shut  the  feed  gates  (or  plates),  the  blocks 
L  are  moved  in  such  a  manner  that  the  claws  Z1  touch  the  shoulders  K1, 
which  are  lifted  and  turn  the  rolls  K,  thus  causing  the  plates  to  drop,  as 
is  shown  on  (5)  and  (6)  Fig.  269.  When  the  gates  are  to  be  opened,  the 
rods  L  are  moved  in  the  opposite  direction,  and  the  shoulders  K1  with 
their  weight  turn  the  rolls  K  back,  thus  opening  the  gate.  As  has  been 
mentioned  above,  the  levers  J1  have  fingers  i*  which  enter  into  the  claws  II 
on  the  blocks  L,  thus  lifting  and  lowering  the  gates  with  the  same, 
motion  that  brings  the  rolls  together  and  apart.  To  keep  this  action  of 
the  apparatus  effective  in  the  operation  of  each  block  separately,  the 
fingers  i2  are  so  arranged  in  respect  to  the  claws  /  that  they  couple  only 


282 


FLOUR   MILLING 


[CHAP,  iv 


if  displaced  from  one  position  to  another.  The  rods  L  are  so  placed  that 
their  ends  are  slightly  raised,  and  when  during  the  movement  of  the  rod 
from  one  side  to  the  other  the  finger  i2  touches  the  claw  /,  the  rod  rises 
and  the  finger  i2  passes  under  the  claw  I  and  stops  between  that  claw  and 
the  one  following  ;  if  the  rod  continues  moving,  the  finger  i2  comes  into 
contact  with  tne  next  claw  I,  and  brings  the  rod  to  a  normal  position 
when  it  is  stopped.  When  the  levers  J1  are  turned  to  one  or  the  other 
side  to  the  extreme  point  (Fig.  269)  5  and  7,  the  fingers  i2  do  not  touch 


A    B 


FIG.  270. 

the  claw  I  at  all,  and  the  rods  L  may  be  moved  backwards  and  forwards 
quite  independently  of  them. 

The  latest  model  examined  of  the  Nordyke  &  Marmon  Co.  mill  is 
shown  on  Fig.  270.  Here  the  adjustable  bearings  H  are  placed  in  the 
middle  and  the  fixed  ones  are  in  the  neighbourhood  of  the  outer  walls, 
and  the  bearings  8  of  the  outer  rolls  are  so  set  as  to  allow  of  regulating 
them,  and  this  is  performed  as  follows  :  the  bearings  8  have  two  tail- 
shaped  arms  a  and  6,  one  of  which,  a,  rests  freely  on  the  bolt  K  screwed 
into  the  arm  L  of  the  frame  ;  the  arm  b  is  fastened  to  the  frame  by  a 
bolt  j  screwed  into  it.  The  planes  of  contact  O  of  the  bearing  and  the 
frame  are  planed  to  each  other  and  determine  the  direction  of  motion 
of  the  bearing.  If  the  bearing  S  is  to  be  lifted  or  lowered,  we  loosen  the 


FLOUR   MILLING 


283 


CHAP.    IV] 

bolt  j  and  turn  the  bolt  K  to  the  right  or  to  the  left.  When  the  axis  of 
the  grinding  roll  is  set  in  a  horizontal  position,  the  bolt  j  is  again  tightened. 
The  adjustable  bearings  H  with  brake  are,  generally  speaking,  constructed 


similarly  to  those  of  the  preceding  model.  The  levers  E  for  throwing 
in  are  eccentrically  set  on  the  hubs  of  the  handles  A  with  toothed  sectors, 
and  their  rolls  are  thrown  together  in  the  required  position.  The  axle  d 
runs  through  the  hopper  and  is  supported  by  bearings  in  brackets  3 
bolted  to  the  arms  of  guards  of  the  fixed  bearings  for  the  axles  of  the 


284 


FLOUR   MILLING 


[CHAP.  IV 


feeding  rolls.  By  means  of  a  screw  with  a  hand-wheel  C,  and  the  hand- 
wheel  D  doing  service  as  a  lock-nut,  the  working  distance  between  the 
grinding  rolls  is  adjusted,  and  the  parallelity  of  their  axes  set.  The 
bearings  of  the  jockey  shaft  are  lifted  by  a  rod  T  which  has  a  square 
thread  and  is  brought  into  motion  by  conic  gears  B.  The  cap  of  the 
bearings  of  the  jockey  shaft  is  kept  on  by  the  bolts  1  and  2.  The  tension 
of  the  spring  is  regulated  by  the  screws  P.  Figs.  271  and  272  illustrate 
the  front  and  the  back  view  of  the  mill.  Fig.  272  clearly  shows  how  the 
feeding  rolls  are  driven  by  belt  gearing.  The"  belt-pulleys  1  and  2  are  set 


FIG.  273. 

on  the  axes  of  the  feeding  rolls  ;  on  the  hub  of  the  bearing  of  the  belt- 
pulley  1  is  set  a  bracket  4  for  the  belt-pulley  3  :  this  bracket  is  joined 
with  a  crank  mechanism  5,  its  crank  set  fast  on  the  axle  d  (see  Fig.  270), 
owing  to  which  at  the  moment  of  throwing  the  rolls  apart  the  belt-pulley  3 
is  drawn  to  the  left,  the  belt  is  loosened,  and  the  feeding  discontinued. 

A  more  simplified  construction  of  simultaneous  lifting  or  lowering  of 
the  jockey  shaft  belonging  to  the  same  works  is  shown  on  Fig.  273,  where 
the  general  hoop  A  carrying  the  bearings  of  the  driving  belt-pulleys  is 
seen.  The  ends  of  the  hoop  rotate  on  journals  fixed  on  the  sides  of  the 
frame,  while  the  middle  has  a  ratchet  stop. 

A  Feed-Crushing  Roller  Mill. — The  feed-crushing  roller  mill  shown  in 


CHAP.    IV] 


FLOUR    MILLING 


285 


Figs.  274  and  275  is  used  by  the  Americans  to  reduce  the  cakes  obtained 
as  a  by-product  in  oil-pressing.  The  rolls  of  such  mills  with  pyramidal 
corrugations  are  cast  in  open-hearth  steel  and  their  surfaces  hardened. 
The  arrangement  of  this  mill  is  very  simple.  The  roll  1  is  set  in  fixed 
bearings,  the  other  roll,  2,  is  placed  in  adjustable  bearings  A,  furnished 
with  a  brake  of  direct  action.  The  bearings  A  have  cylindrical  arms  with 
which  they  are  set  into  the  slippers  B  lying  in  parallel  guides  D.  The 
cups  C  holding  the  springs  are  attached  to  the  frame  by  bolts.  The  ten- 


FIG.  274. 


FIG.  275. 


sion  of  the  spring  is  adjusted  by  bolts.  On  the  reverse  side  of  the  bearings 
there  are  bolts  by  means  of  which  the  distance  between  the  rolls  is  regu- 
lated. 

The  diameters  of  the  rolls  of  such  mills  are  300  to  350  mm.,  their 
length  600  to  800  mm.,  the  number  of  revolutions  of  the  fast  roll  650, 
that  of  the  slow  325,  the  number  of  powers  required  15  to  25. 


(iii.)  Roller  Mills  of  the  Fourth  and  Fifth  Schemes. 

Three-High  Mills. — C.  Kapler's  mill  (Fig.  276)  has  three  grinding 
rolls  wv  w2  and  ws,  placed  diagonally  one  over  the  other.  The  hopper  0 
is  divided  by  a  partition  O2  into  two  chambers.  In  the  lower  part  of 
those  chambers  are  disposed  the  feeding  rolls  al-a2,  to  which  the  gates  m 
approach,  sliding  on  the  outside  surfaces  of  the  inclined  walls  of  the 
feeder.  In  each  gate  m  there  is  a  toothed  rack  m1,  coupling  with  the 
toothed  wheel  l±  on  the  axis  I,  passing  through  the  feeder.  On  the  end 
of  each  axis  I  a  worm  wheel  n  is  freely  set  with  slots  q,  through  which  the 
screws  of  the  stationary  stems  p  at  the  end  of  the  axes  I  can  pass  ;  with 
these  screws  the  wheels  n  may  be  fixed  to  the  stems  p.  The  worm  wheels 
n  are  coupled  up  with  the  screws  ol  on  the  transversal  axis  o  at  one  enc) 


286  FLOUR    MILLING  [CHAP,  iv 

of  the  feeder  ;  on  the  ends  of  this  axis  there  are  hand- wheels.  When 
both  worm  wheels  n  are  fixed  on  the  axes  I  and  the  axis  o  turns,  both  the 
gates  m  accordingly  draw  away  from  the  feed  rolls  al-az  and  the  feed- 
ing in  this  manner  is  regulated  equally  on  both  rolls.  If  it  is  wished  to 
bring  only  one  gate  into  operation,  the  worm  wheel  n  of  the  other  gate 
is  disconnected  with  the  stem  p  or  with  the  axis  I.  On  the  ends  of  the 
axes  of  the  feeding  rolls  al-a2  there  are  set  the  belt-pulleys  R,  through 
which  the  driving  belt  (see  dotted  lines  in  Fig.  3)  runs. 


FIG.  276. 

On  the  opposite  end  of  one  of  the  feeding  roll  axes  there  is  freely  set 
the  belt-pulley  Sl,  which  may  be  connected  with  the  axis  of  the  feed 
rolls  by  means  of  a  toothed  coupling  G.  The  driving  belt  marked  by  a 
dotted  line  on  Fig.  4  passes  over  the  belt-pulleys  Sl  and  S2  on  the  axis  of 
the  top  roll  W±.  Under  the  feeder  two  inclined  plates  7X  and  Y2  are 
arranged.  The  first  supplying  plate  is  placed  over  the  top  roller  W j.  and 
from  the  lower  edge  of  the  plate  Y2  parallel  to  one  side  of  the  chamber  M 
there  runs  a  vertical  partition  e.  An  endless  belt  T1  runs  over  the  feeding 
rolls  n*1,  which  have  a  groove-like  hollow  on  their  circumference,  so  that 
the  middle  part  of  the  belt  lies  lower  than  the  rims  ;  this  belt  runs  parallel 


CHAP,  iv]  FLOUR   MILLING  287 


to  the  middle  grinding  roll  W2  beside  it.  The  feeding  rolls 
lie  inside  the  pockets  c1  and  c2,  which  protrude  at  the  ends  of  the  chamber, 
as  shown  on  Fig.  4.  The  lower  part  of  the  pocket  c2  has  an  incline  and 
forms  a  hopper  c  through  which  the  product  can  flow  out  into  the 
delivery  hopper  d2.  The  axis  of  the  feed-roll  r1  has  a  conic  toothed  wheel 
g1  engaging  the  conic  toothed  wheel  g  on  the  same  axis  with  the  belt- 
pulley  B1  over  which  runs  the  belt  which  passes  likewise  over  the  belt- 
pulley  B  on  the  axis  of  the  middle  grinding  roll  Wz.  The  journal  of  the 
belt-pulley  r2  is  joined  with  a  screw  i  with  the  aid  of  which  the  tension  of 
the  belt  T1  may  be  regulated.  On  the  outer  surface  of  the  roll  W^  there 
rests  a  scraper  61,  on  the  upper  part  of  the  roller  W2  the  scraper  62,  on 
the  lower  part  another  scraper  &3,  and  lastly  close  to  the  side  of  the  roll 
W3  the  scraper  64.  All  those  scrapers  remove  the  product  adhering  to 
the  rolls. 

The  partition  c  has  windows  h3  closed  by  doors  h  opening  to  the  out- 
side, and  fixed  on  joints  to  the  upper  part  of  the  windows.  On  the  inside 
these  doors  have  V-shaped  projections  h1.  When  the  door  is  opened  to  a 
position  shown  on  Fig.  2,  allowing  of  the  insertion  of  one's  hand  through  the 
window  h3  to  get  a  sample  of  the  product  reduced  between  the  upper  and 
the  middle  rolls  W  x  and  TF2,  the  product  falling  on  the  plate  72  opens 
the  gate  h  and  flows  down  the  supplying  plate  /  to  the  nip  of  the  rolls 
W2  and  W3.  A  door  h2  in  the'  wall  of  the  box  affords  an  access  to  the 
windows  h*.  The  shaft  of  the  middle  roll  W2  is  set  in  the  fixed  bearings 
of  the  boxes,  and  the  shafts  of  the  top  and  the  bottom  rolls  Wt  and  W3 
in  adjustable  bearings  supported  by  levers  1  1  fixed  at  the  points  t1  tl  at  the 
ends  of  the  box. 

The  rods  v2  form  eccentric  joints  with  the  axle  v  ;  the  other  ends  of 
those  rods  rest  on  springs  encased  in  the  cups  of  the  levers  of  the  bearings  t. 
The  axle  v  may  be  turned  by  means  of  the  lever  w  moving  on  the  curved 
guide  w1  to  which  it  may  be  attached  by  -a  suitable  screw.  By  turning 
the  shaft  v  one  can  approach  the  bearings  of  the  rolls  W^  and  W3  to  the 
middle  roll  W2  or  remove  them  from  it,  thus  regulating  the  degree  of 
fineness  of  the  grist. 

G.  Daverio's  Three-High  Mill.  —  On  Fig.  277  is  given  the  more  simple 
construction  of  G.  Daverio's  three-high  mill.  The  feed  B  is  divided  into 
two  parts,  every  one  of  which  has  a  separate  feeding  mechanism.  For 
lifting  and  lowering  the  gate  JT  there  is  the  lever  P,  and  a  stop-screw  with 
a  hand-  wheel  C,  for  the  more  accurate  feeding  of  the  product.  The  feed 
roll  of  the  right-hand  side  section  supplies  the  stock  to  the  working  space 
between  the  upper  and  the  middle  roll,  the  roll  on  the  left  serves  the 


288 


FLOUR    MILLING 


[CHAP,  iv 

middle-  and  the  lower  grinding  rolls.  The  rotation  is  communicated  to 
the  feed-rolls  by  a  direct  and  cross-belt  drive  from  the  axis  of  the  top 
grinding  roll  to  the  belt -pulleys  M ,  which  may  be  thrown  off  and  in  by 
hand  with  a  cross-head  coupling  H  with  the  aid  of  the  lever  0.  The 
adjustable  bearing  for  the  lower  grinding  roll  has  a  tail  D,  with  a  cup  for 
the  spring  K.  The  lower  roll  is  thrown  in  and  out  by  the  top  lever  A, 
with  the  aid  of  which  this  roll  may  be  placed  at  any  working  distance. 
A  more  accurate  setting  is  performed  by  means  of  a  hand-wheel  E.  The 

0  tension  of  the   spring  is  ad- 

^£?  justed  by  nuts  on  the  right- 

hand  side  of  the  brake  rod. 
The  top  roll  is  thrown  in  and 
out  by  the  lower  lever  A .  The 
brake  of  this  roll  is  arranged 
similarly  to  the  one  at  the 
top. 

When  this  mill  works  in 
divisions  the  supplying  plates 
are  generally  arranged  as 
shown  on  Fig.  278,  i.e.  the 
product  from  the  upper  and 
the  middle  rolls  passes 
through  the  isolated  open- 
ings in  the  plate  which  directs 
the  stock  to  the  middle  and 
the  lower  roll. 

Wittford's  Three  -  High 
Mill— The  defects  of  the 
three-high  mills  with  rolls 
of  equal  diameter  lies  in  the 
fact  that  the  middle  roll,  in  doing  double  work,  becomes  worn 
more  rapidly  and  requires  a  more  frequent  renewal  of  the  corruga- 
tions. This  causes  a  quick  decrease  in  its  diameter,  an<J  conse- 
quently, the  necessary  differential  of  their  velocities  is  unbalanced. 
An  American  engineer,  Willford,  with  the  view  to  obviating  this  defect, 
recommends  a  mill  with  a  middle  roll  of  double  the  diameter  of 
the  rolls  on  either  side  of  it.  Fig.  279  represents  this  mill,  where  2 
marks  the  frame  of  the  machine,  and  4  the  feed  hopper  with  a  feeding 
mechanism.  The  frame  is  one  cast-iron  block,  while  the  hopper  4  is 
usually  made  of  timber  and  suitably  fixed  to  the  frame.  The  top  and 


FIG.  277. 


FLOUR   MILLINC4 


289 


CHAP.   IV] 

the  bottom  rolls  8  and  10  are  first  placed  into  the  frame  through  the 
middle  aperture  20  in  the  wall,  and  then  pushed  with  journals  into  the 
hollows  22  and  24.  The  middle  roll  3  is  set  in  its  place  between  the  other 
grinding  rolls,  and  the  metal  caps  55 
covering  the  openings  in  the  walls 
are  screwed  to  the  frame.  The  open- 
ings are  made  in  the  opposite  walls 
of  the  frame,  so  that  it  is  possible 
to  put  the  rolls  in  or  take  them 
out  from  either  side,  for  the  mill 
sometimes  has  to  be  erected  in  a 
position  that  would  make  the  rolls 
inaccessible,  if  the  apertures  were  only 
on  the  one  side.  With  this  construc- 
tion all  the  rolls  may  be  inserted 
through  any  particular  opening,  every 
one  of  which  is  sufficiently  large  to 
allow  a  passage  for  the  largest  roll. 

The  hollows  22  and  24  constitute  parts  of  the  opening  20,  but  the 
openings  themselves  may  be  made  so  large  as  to  embrace  the  hollows  too, 
so  that  the  top  and  the  bottom  rolls  or  one  of  them  may  be  put  in,  and 


FIG.  278. 


FIG.  279 

then  pushed  aside  to  give  place  to  the  third  roll.  In  such  a  construction 
the  shape  of  the  opening  20  is  of  no  consequence,  though  the  round 
shape  with  hollows  for  the  journals  of  the  top  and  the  bottom  rolls  is 
preferable. 

The  journals  6  of  the  middle  roll  3  are  set  in  the  bearings^?  in  the  caps  5 


290  FLOUR   MILLING  [CHAP,  iv 

% 
covering  the  openings  20,  which  have  ribs  9  to  impart  greater  strength 

to  the  cap. 

The  journals  of  the  top  and  the  bottom  rolls  are  set  in  bearings,  which 
are  supported  on  levers  15-17,  fixed  by  joints  to  the  walls  of  the  frame 
above  and  below  the  middle  roll. 

The  vertical  bolt  25  passes  through  the  ends  of  each  pair  of  levers. 
In  its  top  part  it  has  a  screw  thread  and  a  hand- wheel  27  with  a  screw 
hub.  Under  the  hand- wheel  there  is  a  washer  29,  and  between  the  washer 
and  the  lever  is  placed  a  spiral  spring  31.  Through  the  front  wall  of  the 
frame,  between  the  ends  of  the  levers,  there  runs  a  shaft  33,  with  cross- 
heads  35,  on  which  the  slide-rods  37  rest.  Those  slide-rods  are  fixed  to 
the  levers  by  screws  39  and  by  adjusting  nuts  41.  The  slide-rods  37  on 
each  lever  are  independent  of  each  other,  and  therefore  by  adjusting  them 
the  parallelity  of  the  roll  shafts  may  be  trammed. 

The  shaft  33  has  a  handle  43  on  one  end,  by  means  of  which  it  can  be 
turned  and  the  ends  of  the  levers  parted  with  the  aid  of  cross-heads,  thus 
forcing  the  top  and  the  bottom  rolls  away  from  the  middle  one.  The 
handle  43  generally  has  a  bracket  45  running  under  the  shaft.  Through 
the  projection  49  there  passes  the  coupling  belt  47  resting  against  the 
bracket  45.  By  turning  this  bolt,  the  position  of  the  rolls  may  be  ad- 
justed. The  rolls  may  be  thrown  apart  by  means  of  a  lever,  and  then 
brought  to  their  primary  position.  The  tension  of  the  springs  31  deter- 
mines the  pressure  of  the  top  and  the  bottom  rolls  upon  the  middle  one. 

The  bearings  for  the  levers  are  formed  on  the  ends  of  the  square  or 
flat  stems  53,  which  pass  through  a  thickening  55  on  the  outer  walls  of 
the  frame  (see  Fig.  4).  By  means  of  bolts  51  and  57  the  position  of  the 
axes  of  rotation  of  the  levers  may  be  altered. 

On  the  shaft  of  the  middle  roll  there  is  set  a  driving  belt-pulley  59, 
with  the  aid  of  which  this  roll  is  driven.  The  surface  of  this  roll  being 
close  to  the  surfaces  of  the  upper  and  the  lower  rolls,  the  latter  are  rotated 
by  friction  with  the  middle  roll,  when  the  stock  flows  between  them  : 
for  this  reason  the  velocity  of  their  rotation  must  be  equal  to  that  of  the 
middle  roll.  To  avoid  this,  there  is  a  separate  differential  belt-drive,  by 
means  of  which  the  velocity  of  rotation  of  the  top  and  the  bottom  rolls  is 
diminished  in  respect  to  the  velocity  of  the  middle  roll.  On  the  opposite 
end  of  the  shaft  of  the  middle  roll  is  set  a  belt-pulley  61.  The  shaft 
of  the  top  roll  has  a  belt-pulley  65,  and  a  similar  belt-pulley  67  is  on  the 
shaft  of  the  bottom  roll.  In  the  plane  of  these  three  belt-pulleys  to  the 
wall  of  the  frame  there  is  fixed  a  lever  71  with  a  hole  at  its  upper  end, 
through  which  there  passes  a  screw  73.  This'  screw  has  a  spiral  spring  75 


CHAP,  iv]  FLOUR    MILLING  291 

between  its  head  and  the  body.  To  the  wall  of  the  frame  there  is  screwed 
a  bracket  77  through  which  this  screw  73  runs.  This  screw  is  provided 
with  a  nut  79  which  rests  against  the  bracket.  In  the  lever  71  the  jour- 
nals of  the  belt-pulley  81  are  fixed.  A  belt  83  runs  to  the  pulley  on  the 
middle  roll,  to  all  the  other  pulleys,  and  to  the  fixed  pulley  81,  as  is 
shown  on  Fig.  2. 

The  lever  71  is  composed  of  two  parts  (Fig.  6),  of  which  one  part,  72,  is 
fixed  on  a  joint  to  the  frame,  and  the  other  part  forms  a  journal  70  enter- 
ing into  the  boss  74  in  the  part  72.  For  coupling  those  two  parts  there 
is  the  bolt  76.  Owing  to  such  an  arrangement,  the  lever  may  be  turned 
on  the  axis,  so  as  to  place  the  belt-pulley  81  in  the  same  plane  as  the  belt- 
pulleys  65  and  67. 

The  Figs.  5  and  6  show  the  construction  of  the  fixed  belt-pulley, 
with  the  aid  of  which  the  motion  of  the  belt  may  be  directed  forwards 
or  backwards. 

The  bearing  boxes  80  for  each  journal  of  the  belt-pulley  81  are  set 
independently  of  the  lever,  and  have  bolts  82  running  through  a  fissure 
in  the  lever,  which  is  opened  in  the  middle  so  as  to  let  a  belt  through  it. 
Each  journal  of  this  belt-pulley  may  be  set  along  the  lever.  By  turning 
the  hand-wheel  79  up  the  belt  is  tightened  on  the  belt-pulleys,  and  the 
belt-pulley  81  communicates  to  the  belt  a  tension  equal  to  that  of  the 
spring. 

The  feed-hopper  91  contains  an  ordinary  feed-roll  93  and  an  ad- 
justable gate  95.  In  addition  there  is  a  device,  by  means  of  which 
the  feed  may  be  stopped  without  displacing  the  feed  gate.  This 
appliance  consists  of  a  metal  plate  97  which  may  be  stationed  across  the 
lower  part  of  the  hopper,  forming  a  bottom.  This  bottom  is  connected 
with  the  crank  99  furnished  with  heads  101,  the  journals  of  which  enter 
into  the  walls  of  the  hopper.  On  the  outside  of  the  frame,  to  one  of  these 
heads  is  attached  a  handle  102.  By  moving  this  handle,  the  bottom  may 
be  brought  to  the  position  marked  by  dots  (see  Fig.  3) ;  in  this  position 
the  plate  lies  parallel  to  the  walls  of  the  hopper  and  does  not  impede  the 
passage  of  the  stock. 

/.  B.  Allfree's  Four-High  Mill. — For  three  succeeding  passages  of 
the  product  the  use  of  four -roller  mills  is  suggested,  one  of  which  (of 
American  construction)  is  shown  in  Fig.  280. 

The  frame  A  has  vertical  arms  B.  To  those  arms  the  bearings  C 
supporting  the  fixed  grinding  rolls  DD  are  fixed.  These  bearings  are 
fastened  to  the  arms  by  bolts  a  ;  at  the  lower  ends  there  are  coupling 
bolts  b  with  the  aid  of  which  the  bearings  may  be  adjusted,  because  those 


292 


FLOUR   MILLING 


[CHAP,  iv 


bolts  rest  against  a  projection  on  the  frame  made  for  that  purpose.  On 
the  other  side  of  the  vertical  arm  there  are  fixed  in  suitable  positions  two 
L-shaped  brackets  E  supporting  truckle  axles  F,  which  run  through  the 
whole  frame,  with  necks  at  either  end,  protruding  beyond  the  brackets. 
These  brackets  are  eccentric  in  respect  to  the  body  of  the  shafts,  and  their 
duty  is  to  support  the  adjustable  bearings  G  for  the  rolls,  and  also  the 
levers  H  at  the  other  end. 

In  the  upper  parts  of  the  L-shaped  brackets  E  there  are  vertical  slots 
(dotted  out  e  on  Fig.  6),  through  which  the  coupling  bolts  /pass.  These 
brackets  have  adjusting  screws  g  for  setting  the  rolls  in  a  parallel  position, 


Pro.  280. 

at  one  end,  and  a  long  horizontal  opening  J  (see  Fig.  6),  the  inner  end  of 
which  is  rounded,  so  that  the  shaft  F  may  pass  into  it.  A  small  bush  h, 
with  a  cavity,  on  the  side  adjacent  to  the  shaft  F  (Fig.  7)  is  set  into  the 
slot ;  this  bush  can  freely  slide  in  the  slot.  It  is  held  in  its  position  by  a 
small  spiral  spring  i  to  which  the  desired  tension  may  be  imparted  by 
means  of  a  screw  j  running  through  the  end  of  the  bracket  and  resting 
against  the  spring.  The  spring  i  with  the  bush  sliding  in  the  slot  serves 
as  an  elastic  stop  to  the  truckle  shaft  F  ;  the  eccentric  end  of  this  shaft 
passes  through  one  of  the  ends  of  the  adjustable  bearing  G  for  the  rolls, 
which  is  fixed  to  the  neck  of  the  shaft,  so  that  in  the  case  of  a  hard  body 
falling  in  between  the  rolls,  they  can  move  apart,  owing  to  the  action  of 
the  truckle  shaft  F,  the  bushes  h,  and  the  spring  i.  The  other  ends  of  the 
roll-bearings  are  supported  and  adjusted  by  screws  k  with  forked  ends 


CHAP,  iv]  FLOUR   MILLING  293 

running  from  the  middle  arm  through  an  opening  in  the  ends  of  the  bear- 
ings G.  On  these  screws  there  are  set  hollow  coupling  nuts  I  which  are 
on  the  outside  of  the  walls  of  the  machine  and  serve  to  bring  the  rolls 
together  and  apart,  with  the  view  to  obtaining  a  product  of  the  desired 
fineness.  Between  that  part  of  the  roll-bearing  through  which  the  screw 
bolt  passes  and  the  middle  arm  B,  a  spiral  spring  m  with  a  nut  and  a  washer 
behind  it  is  placed.  The  purpose  of  this  spring  is  to  hold  the  roll-bearings 
in  the  position  required,  so  that  the  rolls  should  not  become  worn,  when 
there  is  no  product  between  them. 

If  it  is  wished  to  throw  the  rolls  apart  at  a  moment's  notice,  the  truckle 
shafts  F  are  turned  by  means  of  the  handles  H  fixed  to  the  ends  of  those 
shafts.  By  turning  the  shafts,  the  roll-bearings  G  supported  by  the 
eccentric  necks  of  the  shafts  are  moved.  The  handles  H  are  connected 
with  each  other  by  a  stem  K)  one  end  of  which  is  fixed  to  one  handle,  and 
the  other  passes  through  the  tension  bolt  coupled  with  the  other  handle  ; 
in  this  wise  the  position  of  one  handle  may  be  adjusted  in  respect  to  the 
other  one.  One  of  these  handles  H  is  held  in  any  unchangeable  position 
by  a  lock  screw  with  a  nut,  passing  through  the  segment  link  L,  which  has 
its  upper  end  fastened  by  a  joint  to  the  frame  of  the  machine,  so  that  this 
link  is  sufficiently  loose  to  allow  the  roll-bearings  G  to  move  away  when  a 
hard  body  is  caught  between  the  rolls. 

M  is  an  ordinary  American  jockey  shaft. 

To  the  top  of  the  frame  any  kind  of  a  feeding  mechanism  may  be 
adapted.  The  grinding  rolls,  as  is  seen  on  Fig.  2,  consist  of  two  fixed,  Z>, 
and  two  adjustable  rolls,  D' '. 

Inside  the  frame,  parallel  to  the  rolls,  there  are  placed  three  feed 
plates,  N,  N',  and  N".  The  top  shelf  N  directs  the  grain  flowing 
from  the  feeder  into  the  space  between  the  fixed  top  roll  D  and  its 
adjustable  neighbour  D'.  Having  passed  to  the  opposite  surfaces  of 
those  rolls,  the  reduced  grain  is  conducted  by  the  plate  Nf  to  the 
working  space  between  the  upper  adjustable  roll  .D'  and  the  second 
fixed  roll  D.  After  this  passage  its  flow  is  deflected  by  the  plate  N"  to 
the  space  between  the  fixed  bottom  roll  D'  and  then  pours  down  as 
shown  by  arrows. 

The  top  shelf  N  is  stationary,  the  other  two,  JV'  and  N",  have  joints 
below,  shown  in  n,  and* their  upper  edges  are  joined  by  a  slewing  head  P 
with  a  fixed  rack  0,  so  that  when  it  is  necessary  to  examine  the  pro- 
duct, the  plates  N'  or  N"  may  be  lowered  after  loosening  the  slewing 
head,  and  the  product  then  passes  through  corresponding  doors  into  the 
frame,  sliding  down  the  inclined  plate. 


294 


FLOUR   MILLING 


[CHAP,  iv 


(iv.)  Roller  Mills  of  the,  Eighth  Scheme 

W.  Gray  and  R.  Birkholtz's  Four-Roller  Mill. — The  roller  mills  of 
European  constructions  for  successive  passages  of  the  eighth  scheme 
(p.  214)  represent  the  ordinary  types  of  two-roller  mill  with  the  shafts 
of  the  corresponding  pairs  of  rolls  lying  in  a  vertical  plane.  The  number 
of  passages  is  from  two  to  four,  and  this  process  is  performed  in  plain 
milling  or  the  milling  of  feed  stuffs.  Of  those  mills  we  shall  examine  the 
American  construction  of  W.  Gray  and  Birkholtz,  as  the  most  original. 


FIG.  281. 


This  mill  is  shown  in  Fig.  281.  The  rolls  EG  of  each  pair  are  set  in 
fixed  bearings,  the  other  two  rolls  DD'  in  adjustable  bearings  with  tail 
frames  and  brakes  already  familiar  to  us.  The  bearings  have  ball-arms 
(Sellers'  type)  for  self-adjustment,  and  on  the  lower  side  they  have  longi- 
tudinal arms  e2  with  which  they  drop  into  the  slides  D  and  prevent  the 
bearings  from  rolling  out  of  their  seats. 

The  bearings  are  held  in  their  set  positions  by  screws  e3  screwed 
into  the  arms  e4  which  hang  over  the  bearings.  The  position  of  e4 
is  such  as  to  allow  of  removing  the  bearing  from  its  place, 
once  the  screw  has  been  loosened.  For  this  purpose  the  hollow  is  left 
open  on  one  side,  and  its  shape  is  such  that  whilst  the  box  or  the  bearing 


CHAP.    IV] 


FLOUR   MILLING 


295 


has  a  solid  stay  on  the  lower  and  the  outer  sides,  which  carry  the  pressure 
of  the  journals,  the  box  may  be  easily  removed  by  lifting  it  up  and  out. 
This  means  of  supporting  the  bearings  has  proved  in  general  practice  to  be 
very  convenient,  as  it  affords  the  possibility  of  removing  any  one  of  the 
adjustable  rolls,  together  with  its  bearings,  at  a  moment's  notice,  without 
touching  anything  in  the  mill. 

The  rolls  are  brought  into  operation  by  means  of  belts  and  belt-pulleys 
in  the  following  manner.  The  jockey  shaft  passes  through  the  lower  part 
of  the  mill  from  one  wall  to  the  other,  resting  in  bearings  fixed  in  the  frame 
J.  One  end  of  the  shaft  carries  a  belt-pulley  i,  the  other  end  two  belt- 
pulleys  il  and  i2.  The  fixed  rolls  B  and  G  have  belt-pulleys  b  and  c  on 
the  same  side  as  the  belt -pulleys  il  and  i2  » 

are  placed.  The  adjustable  rolls  B'  and  C' 
have  belt-pulleys  b'  and  c'.  The  driving  belt  T 
runs  through  the  belt-pulley  c'  under  the  belt- 
pulley  i  of  the  jack-shaft  and  above  the  belt- 
pulley  b',  bringing  directly  into  action  both  the 
adjustable  rolls  and  the  jack-shaft.  From  the 
belt-pulley  il  of  the  jack-shaft  the  belt  b2  passes 
to  the  belt-pulley  c  and  rotates  the  fixed  bottom 
roll,  while  another  belt  c2  runs  to  the  belt- 
pulleys  iz  and  b  rotating  the  fixed  top  roll.  For 
such  an  arrangement  of  the  belts  and  belt- 
pulleys,  it  is  necessary  that  the  lower  rolls 
should  be  moved  aside,  owing  to  which  the 
belts  and  belt-pulleys  may  operate  freely,  occupying  at  the  same  time 
little  space. 

For  an  accurate  adjustment  of  the  rolls,  and  the  possibility  of 
quickly  throwing  them  apart  and  together,  W.  Gray's  construction, 
already  examined,  has  been  adapted.  The  upper  and  the  lower  rolls  are 
simultaneously  thrown  apart  and  together  by  means  of  a  handle  K  fixed 
to  the  lower  roll  c6  with  an  eccentric  and  connected  through  a  stem  k 
with  the  crank  kl  on  the  top  roll  66. 

For  regulating  the  feeding  of  the  mill,  in  the  hopper  L  there  is  (Fig.  282) 
on  one  side  a  movable  gate  I  which  may  be  moved  in  a  vertical  direction. 
The  bottom  in  the  hopper  is  a  shaking  inclined  toothed  plate  m  placed 
above  the  top  roll  and  attached  to  the  top  part  of  the  shaking  shoe  M , 
to  which,  under  the  bottom  rolls,  is  fixed  another  inclined  plate  m'  of 
greater  breadth.  The  shoe  consists  of  two  iron  sideplates  m3  fixed  to  the 
edges  of  the  feeding  plates  and  strengthened  by  suitable  cross  pieces. 


FIG.  282. 


296  FLOUR   MILLING  [CHAP,  iv 

On  the  one  side  the  shoe  is  supported  by  one  or  several  belts  m4  attached 
by  their  upper  ends  to  the  frame  ;  at  the  front  edge  it  is  supported  by 
one  or  several  belts  or  wires  m5  also  attached  to  the  frame  ;  the  shoe  can 
move  in  a  direction  perpendicular  to  the  shafts  of  the  rolls.  This  motion 
is  communicated  to  it  by  means  of  two  eccentric  drives  m6-m7  from  the 
general  axle,  receiving  the  motion  with  the  aid  of  a  belt-pulley  set  on  it, 
and  connected  by  a  belt  m8  with  the  pulley  on  the  axle  of  the  roll  C' . 
The  feeding  top  shoe  passes  under  the  flap  valve  of  the  hopper  and  con- 
veys the  stock  from  the  bottom  part  of  the  hopper  to  the  fixed  supplying 
plate  n,  which  directs  it  to  the  working  space  of  the  rolls.  Having  passed 
through  the  top  rolls  the  stock  falls  on  the  lower  feeding  plate  w'  which 
directs  its  course  to  the  second  pair  of  rolls. 

To  prevent  the  product  from  falling  in  behind  the  shoe,  a  piece  of 
lining  I"  is  attached  to  the  back  wall. 


7.  Transmission  of  Motion  to  the  Rolls 

Toothed  Gearing. — We  have  already  examined  the  details  of  the  roller 
mills  having  a  special  function — the  feeding  and  the  adjustment  mechan- 
isms, for  instance.  Now  we  must  note  the  details  of  a  general  character, 
which  are  of  no  less  importance  than  the  feeding  and  the  brake  devices. 

Of  the  details  of  a  general  character,  the  parts  of  machinery  trans- 
mitting the  motion  are  the  most  important.  In  our  general  review  of 
roller  mills  we  have  noted  that  there  are  two  types  of  gearing  :  the  toothed 
gearing  adopted  by  the  European  engineers  and  partly  in  American 
mills  for  rough  grinding  (the  reduction  of  forage  products),  and  the  belt- 
gearing  employed  by  the  Americans  only.  Here  we  are  speaking  of 
transmitting  the  motion  from  roll  to  roll.  To  communicate  motion  to 
the  feeding  rolls,  the  European  engineers  generally  use  combined  gearing, 
the  flexible  and  the  toothed,  while  the  Americans  employ  only  the 
former  in  their  mills  of  the  latest  type. 

Consider  the  toothed  gearing  given  in  Fig.  283  (1,  2  and  3).  The 
first  one,  the  simplest,  is  used  for  mills  of  small  capacity,  and  in  cases 
where  the  degree  of  evenness  plays  no  great  part.  The  second  type  of 
toothed  gearing  represents  doubled  chain  wheels  with  a  chess-board-like 
disposition  of  the  teeth  to  lessen  vibration  in  working.  It  has  been 
adopted  by  some  of  the  American  works.  The  ordinary  toothed  gearing 
with  a  helical-like  disposition  of  the  teeth,  shown  on  3,  has  been  adopted 
by  almost  all  works.  In  this  last  gearing  the  wheels  are  provided  with 


CHAP,  iv] 


FLOUR   MILLING 


297 


ring  lubrication,  used  by  Seck's  works  and  by  the  American  works  of 
Wolf  (both  patents  were  claimed  simultaneously). 

In  speaking  of  the  merits  of  toothed  gearing  the  accuracy  it  attains 
in  the  ratio  of  gearing  must  be  pointed  out.  But  the  grave  defect  of  the 
toothed  gearings  in  the  roller  mills,  where  the  distance  between  the 


FIG.  283. 

shafts  has  to  be  altered,  is  the  decreased  efficiency  when  in  operation  and 
the  shafts  have  to  be  brought  nearer  to  each  other  in  proportion  to  the 
wear  of  the  rolls.  The  necessity  of  altering  the  distance  between  the 
axles  of  the  gears  demands  an  outline  of  the  teeth  according  with 
the  involute  of  the  circle.  Under  our  conditions,  however,  the  axes 
of  the  wheels,  in  the  most  favourable  circumstances,  may  only  be 
brought  10  mm.  nearer  than  the  normal.  Consequently  the  wear 


298 


FLOUR    MILLING 


[CHAP,  iv 


and  renewal  of  the  working  surfaces  may  go  only  5  mm.  deep  for  each 
roll,  otherwise  the  toothed  gearing  will  be  operating  at  a  great  disadvan- 
tage. Thus,  if  each  of  the  rolls  has  worn  5  mm.,  new  gear  wheels  with 
smaller  diameters  have  to  be  installed,  otherwise  the  gear  will  cause  a  great 
waste  of  power.  In  Russian  mills  this  is  generally  not  taken  into  con- 
sideration, and  economising  in  new  pinions  the  work  is  performed  till  the 
teeth  break,  regardless  of  the  fact  that  more  is  lost  in  the  expenditure 
of  energy,  and  the  fact  that  the  motor  has  to  be  overloaded  without 
increasing  the  capacity  of  the  mills  is  regarded  with  surprise. 

Thus  the  expediency  of  the  toothed  gearing  may  be  acknowledged, 
but,  when  the  rolls  are  in  working  position,  the  axes  of  the  pinions  can 

only  at  most  be  brought 
nearer  together  by  about 
10  mm.  If  the  distance 
between  them  is  to  be 
still  further  decreased, 
the  pinions  must  be 
changed. 

Belt-gearing.  —  Several 
of  the  belt-gearing  con- 
structions were  dealt  with 
when  describing  the 
makes  of  American  mills. 
The  shafts  of  the  driving 
belt-pulleys  are  usually 
attached  to  the  frame. 
But  often,  to  simplify 
the  construction  of  the  mill,  they  are  stationed  outside  and  apart,  as 
shown  in  Fig.  284.  Here  B  is  the  axle  of  the  shafting,  C  the  jockey- 
shaft,  1  the  driving  belt  to  the  fast  rolls,  and  2  to  the  slow.  The  tension 
of  the  belt  is  adjusted  by  toothed  gears  A,  and  the  supplementary  regula- 
tion of  tension  of  the  belts  to  the  slow  rolls  is  brought  about  by  lowering 
or  raising  the  bearing  by  screws  3. 

Some  twenty  years  ago,  when  the  European  engineers  attempted  to 
introduce  belt-gearing,  the  principal  argument  against  it  was  the  impossi- 
bility of  maintaining  an  accurate  number  of  revolutions  of  the  rolls, 
owing  to  the  belt  slipping.  The  work  of  the  American  mills  of  the 
contemporary  makes,  however,  proved  that  this  argument  had  no  solid 
ground  under  it.  The.  slipping  of  the  belt  within  such  limits,  as  to 
affect  the  accuracy  of  the  transmitted  number  of  revolutions  of  the 


FIG.  284. 


CHAP.   IV] 


FLOUR   MILLING 


299 


rolls,  is  possible  when  the  belt  has  stretched  and  its  tension  consequently 
has  slackened.  But  the  American  construction  of  belt-drives  obviates  this 
defect  by  regulating  the  tension.  The  presence  of  an  insignificant  slipping 
motion  cannot  be  denied,  but,  as  we  have  seen,  the  ratio  of  velocities  of 
the  fast  and  the  slow  rolls  for  every  break  and  reduction  passage  is 
within  certain  limits ;  while  the  influence  of  the  slipping  is  so  in- 
significant, as  shown  by  practice  in  America,  that  these  limits  are  never 
exceeded. 

The  advantages  the  American  belt-driving  has  as  against  toothed 
gearing  are  very  material,  viz.  : 

(1)  Noiseless  and  easy  run  of  the  mill. 

(2)  No  relacing  of  the  belt  in  case  it  becomes  extended  is  required, 
the  tension  being  regulated  by  a 

jockey-pulley. 

(3)  The  reserve  strength  of  the 
belt  being  sufficiently  great,   the 
capacity  of  each  mill   separately 
may  be  increased  by  10  to  20  per 
cent,  by  a  corresponding  increase 
in  the  tension  of  the  belt. 

The  latter  is  very  important,  as 
it    permits   overloading    the   mill  FlGt  285. 

without   any    injurious    effect    to 

the  quality  of  the  work,  which  cannot  be  attained  on  European  roller 
mills,  as  the  tension  of  the  gear-belt  from  the  shafting  axle  to  the  mill 
cannot  be  altered  without  relacing  the  belt. 

In  some  mills  with  belt-gearing  each  roll  has  a  separate  belt-pulley,  as 
shown  in  Fig.  285.  The  necessity  of  compactly  disposing  the  belt-gearing 
leads  to  setting  the  fast  rolls  asymmetrically. 


8.  Capacity  of  Roller  Mills 

Useful  Work  of  Roller  Mills. — In  examining  the  action  of  the  work- 
ing organs  in  the  roller  mills,  we  saw  that  a  rather  complicated  process  of 
cutting  the  grain  on  break  rolls  or  chipping  by  friction  of  the  particles 
on  reduction  rolls  is  performed.  Therefore  the  useful  work  of  the 
roller  mill  may  be  defined  only  by  experiment.  However,  the  attempts 
to  evolve  theoretic  formulae  of  useful  work  which  partly  explain  the  pro- 
cess of  milling,  and  partly  may  have  a  practical  effect  through  the  intro- 
duction of  practical  coefficients  into  them,  should  receive  due  attention. 


300 


FLOUH  MILLING 


[CHAI*.    IV 


The  first  and  sole  attempt  to  give  theoretic  formulae  of  the  useful 
work  of  the  roller  mills  was  made  by  Professor  Afanasyeff  ,l  and  was  based 
on  his  experiments  on  the  resistance  of  the  grain  to  pressure,  performed 
at  the  mechanical  laboratory  of  the  Technological  Institute,  St.  Peters- 
burg. Repeated  experiments  with  the  resistance  to  pressure  of  grains 
(200  grains  or  more  each  time)  of  a  normal  moisture  content  and  of  approxi- 
mately equal  size,  placed  in  between  steel  plates  under  a  press,  produced 
the  following  results  : 

TABLE   XXV 


Pressure  in  Klgs. 

0 

1000 

2000 

3000 

4000 

5000 

Distance  between  the  plates  | 
(thickness  of  the  grain)  in  !• 

2-723 

2-395 

2-068 

1-753 

1-542 

1-391 

mm.     J 

Compression  in  successive) 
loadings    / 

... 

0-328 

0-327 

0-315 

0-211 

0-151 

This  table  shows  that  the  absolute  quantity  of  elastic  pressure  is  equal 
to  one-third  of  the  size  of  the  gram. 

The  full  loading  up  to  the  limits  of  elasticity  of  the  grain  fluctuated 
between  10  and  20  klg.  to  each  grain  in  proportion  to  its  moisture  content, 
the  less  limit  referring  to  the  grain  with  more  moisture.  This  corresponds 

to    the   loading    of    50    to    100    klg.   to    1 
square  cm. 

In  defining  the  law  of  changing  the 
pressure  of  the  rolls  on  the  grain  or  particles 
of  it,  Professor  Afanasyeff  reasoned  in  the 
following  manner  :  supposing  we  have  two 
rolls  of  equal  radii  r  (Fig.  286)  with  the 
distance  between  the  working  surfaces  £  and 
the  size  of  the  stock  to  be  treated  £0. 
Suppose  that  the  pressure  of  the  rolls  upon  the  stock  on  the  route  it 
travels  from  n  to  nl  is  proportionate  to  its  compression.  If  we  mark 
the  quantity  of  the  pressing  forces  along  the  centre  line  P,  and  Q  is  some 
intermediate  position  of  the  stock  u-u,  then  Q  is  defined  from  the 
proportion  : 

Q:P=su:qn1 (l), 


FIG.  286. 


1  Flour  Mills,  St.  Petersburg,  1883. 


CHAP,  iv]  FLOUR   MILLING  301 

for  the  pressures,  when  the  compression  is  elastic,  are  proportional  to 
the  quantities  of  compression  (2  su  and  2qn1)  being  pressed  from  two 
sides.  But  since 


while  in  the  drawing 

£0=2r-|-$  — 2r  cos  a— £=2r(l—  cos  a), 

having  performed  the  reductions  and  the  substitution  1— cos  a =2  sin2^, 
we  obtain  : 

qn1=2r  sin2  ~. 
A 

From  the  same  drawing  we  obtain  the  signification  of  su  for  the  inter- 
mediate position  of  the  stock  : 

su = 2r  sin2  ^  —  2r  sin2  ^. 

By  substituting  these  senses  into  the  formula  (1)  we  obtain  : 

sin2-  — sin2- 


The  angles  a  and  6  being  very  small,  with  a  slight  inaccuracy  we  may 
regard  the  sines  as  equal  to  the  circular  measure  of  these  angles.  Then 
we  have  : 

«-*¥• 

That  is  the  pressure  of  a  unit  of  area  of  the  roll,  whereas  we  are  to  find 
the  pressure  from  n  to  %  so  as  to  know  the  full  work  of  the  pressure.  If 
the  element  u±u  of  the  surface  of  the  roll  corresponds  to  the  angle  do, 
and  the  dimensions  uul  on  the  generating  circle  of  the  cylinder  is  I,  the 
elementary  pressure  will  be  : 

^de  .     ;    .     (2). 

The  full  pressure  R  is  obtained  when  we  take  the  integral  of  this  term 
from  a  to  o. 


The  point  of  application  of  this  resultant  pressure  is  obtained  on  our 
defining  the  moment  of  action  of  this  force.     The  moment  of  action  dQ  is  : 


302  FLOUR   MILLING  [CHAP,  iv 

for  up=r  sin  6  =  rO,  the  6  being  small.  By  integrating  this  term,  we 
arrive  at  the  moment  of  the  compressing  force  R  in  respect  to  the  axis 
of  the  roll  : 


On  dividing  (4)  by  (3)  we  obtain  the  shoulder  of  the  resultant  of  the 
pressures,  by  which  we  shall  define  the  point  of  application  of  force  R. 
This  shoulder  77  will  be  : 

rj=\ra. 

If  we  distribute  these  R  directed  parallel  to  the  plane  of  the  axes, 
over  the  tangent  and  the  radius  (Fig.  287),  we  shall  obtain  : 

3   _3,?       p      p        3       3~ 
8a-8^a;  X2-         >Sga-g^, 

^     because  the  angles  a  being  small,  we    may 
accept 

o          o  O 

sin-a=-aand  cos5a=l. 

1  •  o  O  o 

Then  the  motive  power  of    each    roll, 

imparting  velocity  to  the  product  during  the  period  from  the  null  sense 
to  the  greatest  v,  equal  to  the  rotating  velocity  of  the  rolls,  will  be 


But  this  moment  is  so  insignificant  that  we  may  ignore  it  and  con- 
sider the  velocity  of  motion  of  the  product  between  the  rolls'  from  the 
beginning  of  its  ingress  to  its  exit  to  be  even  and  equal  to  the  rotary 
velocity  of  the  rolls.  These  considerations  prevent  our  accepting  as 
correct  Professor  AfanasyefTs  inference,  who  regards  S=fR2  —  Ri  as  the 
motive  power  and  further  defines  the  work  of  the  roller  mills  as  the  work 
of  this  force  8. 

The  work  of  the  forces  fR2  must  be  defined  by  taking  their  projection 
upon  the  direction  of  the  motion  of  the  product,  i.e.  upon  the  vertical 
plane. 

Then  the  sense  of  the  motive  power  will  be  : 


Professor    Afanasy  eft's    experiments     have     shown    that    P=4*5^, 
where   d  means  the  thickness  of  a    grain  of  wheat,  and  p  the  relative 


CHAP,  iv]  FLOUR   MILLING  303 

£  —  £ 
compression  equal  to  ^—2.     Availing  himself  of  Professor  AfanasyefFs 

experimental  data  (P=k5-  —  the  average  for  dry  grain)  and  introducing 

a  correction  with  regard  to  the  incomplete  utilisation  of  the  working 
surface  of  the  rolls,  Professor  Zworykin  suggests  the  following  term  for 
the  efficiency  of  the  rolls  : 

Plra  Plra*v 


where  r  denotes  a  k-ih  part  of  the  rolls  loaded  with  product  on  the  arch 

K 

nn-i,  and  7~the  A-j-th  part  of  rolls  over  their  length. 
#1 

We  must  acknowledge  this  correction  to  be  just,  as  the  working  part 
of  the  rolls  is  not  fully  occupied  with  product. 

Then,  knowing  that 


we  introduce  those  terms  into  T.    Thus  we  obtain  : 

'        0-25  to 


In  this  formula  T  is  expressed  in  klgr.-mtrs.,  I  in  mm.,  and  v  in 
metres  per  second. 

This  formula  leads  Professor  Zworykin  to  the  conclusion  that  the 
consumption  of  useful  work  for  crushing  the  product  fed  in  at  a  certain  flow 
does  not  depend  on  the  diameter  of  the  rolls,  but  solely  on  its  circumferential 
velocity  and  length. 

According  to  Professor  Kick's  experiments,  who  was  testing  soft 
wheat  the  grains  of  which  were  6  to  7  mm.  long  and  3*5  mm.  thick,  the 
force  crushing  the  grain  while  it  is  moving  over  1  mm.  of  ground  is  10  klg. 
Consequently,  the  work  of  crushing  the  grain  ought  to  be  0*005  klg.- 
mtr.  per  second. 

To  define  the  consumption  of  useful  work  according  to  the*  data  of 
Professor  Kick,  we  must  know  the  number  of  grains  crushed  per  second 
and  multiply  it  by  0*005.  If  the  working  surface  of  the  roll  running  by 
per  second  should  be  given  in  square  mm.,  it  is  equal  to  1000  Iv,  The 


304  FLOUR    MILLING  [CHAP,  iv 

area  of  the  grain  is  6'  5x3*  5  mm.  Then,  with  Professor  Zworykin's 
correction,  we  obtain  : 

0-005.  1000  lv_  0'22  Iv 
~~6-5x3'5fc.  ki~~     kk1    '• 

which  closely  resembles  the  results  produced  by  Professor  Afanasyeff's 
investigations. 

Consumption  of  Useful  Work  in  Grinding.  —  The  considerations  of 
Professors  Afanasyeff  and  Zworykin  we  have  adduced  have  a  purely 
theoretical  value.  Those  formulae  elucidate  the  general  character  of 
the  phenomenon  but  cannot  be  adapted  to  define  the  useful  work  of  the 
roller  mills,  being  deduced  on  the  supposition  that  the  rolls  have  equal 
velocities,  which  never  happens  in  reality.  The  equal  velocities  of  the 
rolls  result  in  the  crushing  of  the  stock,  whereas  a  cutting  or  chipping 
of  the  grain  or  particles  of  it  is  observed  when  the  velocities  are  different. 
Thus,  to  define  the  useful  work  in  reducing  it  is  necessary  to  know  the 
resistance  to  cutting,  which  requires  an  immediate  experimenting  on 
the  cutting  of  grain.  By  this  reason,  having  no  other  data,  Professor 
Zworykin  suggests  making  use  of  Professor  Kick's  experiments  and 
evolves  a  series  of  formulae  defining  the  useful  work. 

According  to  Professor  Kick's  researches  the  resistance  to  the  cutting 
of  the  grain  increases  from  0  to  9  klg.  on  the  stretch  of  0'5  mm.  ;  there- 
fore the  cutting  work  for  one  grain  is  equal  to  0*00225  klg.-mtr.  Ac- 
cepting for  the  break  rolls  the  circular  pitch  of  the  corrugation  to  be  t, 
the  velocity  of  the  fast  roll  v,  and  its  length  I,  we  obtain  that  the  number 
of  grains  passing  between  the  rolls  per  second  is 

1000  Iv 


As  the  circular  pitch  of  the  corrugation  t  must  correspond  to  the 
dimensions  of  the  stock  cut,  t  =  kld  =  k13'5,  consequently  the  useful 
work  T  for  corrugated  rolls  will  be  expressed  thus  : 


For  smooth  roller  mills  the  useful  work  will  be  expressed  by  the 
formula  : 


"'• 


These  formulae  may  become  very  valuable,  if  through  the  immediate 
definitions  of  the  useful  work  of  the  roller  mills  with  different  I,  v,  and  t 


CHAP,  iv]  KLOUR    MILLING  305 

(t  is  needed  for  corrugated  rolls)  we  find  by  experiment  the  coefficient 

1 

fCiC  i 

Theoretical  Capacity  of  Roller  Mitts. — Proceeding  from  the  foregoing 
inferences,  we  may  mention  several  considerations  regarding  the  theo- 
retical capacity  of  roller  mills. 

If  the  thickness  of  the  sheet  of  product  flowing  into  the  nip  of  the 
rolls  be  mark  d,  then  its  volume  passing  in  between  the  working  surfaces 
is  (with  the  same  denominations  of  I,  v,  k,  and  k±  as  before)  : 

1000  I .  v .  d 


V  = 


kk1 


Accepting  the  specific  gravity  of  the  stock  to  be  0*0000006  klg.,  we 
obtain  the  weight  Q: 

.  0-0000006=°-^^  (8). 


Thus  we  see  that  the  capacity  of  a  roller  mill  is  a  rather  complicated 
function  of  five  variables.  Given  the  length  of  the  rolls  and  the  circum- 
ferential velocity  of  the  fast  roll,  we  may  accept  Iv  for  this  mill  as  a  con- 
stant quantity.  Then  the  problem  of  defining  the  capacity  is  simplified, 
for  the  capacity  will  depend  on  6,  k  and  kv  These  variables  depend  on 
the  kind  of  milling,  which  determines  what  their  respective  values  are  to 

be.  But  it  is  impossible  to  give  any  limiting  values  for  TT-,  because  the 
milling  diagrams  are  very  variously  arranged.  Since  we  have  no  serious 
experimental  data  for  jj-  as  yet,  we  are  compelled  to  make  use  of  the 

A/n/i 

data  of  capacities  of  roller  mills  as  given  by  the  works,  with  corrections 
founded  on  general  observations  of  the  capacity  of  these  machines  at 
modern  mills. 

Practical  Data  of  the  Capacity  of  Roller  Mills.  —  The  capacities  of 
break  and  reduction  roller  mills  given  below  were  taken  from  the  data 
of  European  works  tested  on  the  plants  in  Russian  mills,  on  milling 
systems,  which  are  duly  mentioned  in  the  table.  Naturally  the  factory 
data  fairly  accurately  coincided  with  the  capacities  observed  at  the 
mills,  for  the  builders  of  these  mills  more  or  less  strictly  adhered  to 
their  data.  Very  often,  however,  the  capacity  of  one  or  another  mill 
exceeded  the  guarantees  of  reliable  works  ;  this  is  always  the 
result  of  overloading  the  machines  at  the  expense  of  the  quality  of 
the  work, 

IT 


306 


FLOUR    MILLING 


[CHAP,  iv 


X 


PQ 
<! 

H 


P 
fc 

2 

GO 

I 

O 


S 


s 

o 


3 

H 

1 

g 

< 


J! 


i 


§ 


sumption  in 
mm.  length 


er  cons 
per  100 
ir  of  roll 


Pow 
.R 


H. 

of 


iO  <^>  ^O  O  ^^ 


8^^  O  O  O1 
o  o  ^^  *o 
^  »o  co  t-  i>- 


I 


Hill  III 


8 


O  O  O  O  O 


O        O  O  O  O 


8888 


88|| 


l>  O5  (M 

i-i  rH  c?q 


O  O1  O  ^D  O1 
J>*  00  O5  G1^  G*l 


FLOUR    MILLING 


307 


CHAP.    IV] 

In  the  Table  XXVI  given  opposite  the  average  capacity  and  power- 
consumption  are  taken  from  the  factory  data. 

The  data  of  that  table,  regarding  the  breaking  process  (corrugated 
rolls),  refers  to  the  first  passage  or  break.  The  capacity  of  the  smooth 
rolls  refers  to  the  reduction  of  coarse  and  fine  middlings,  and  is  to  be 
taken  at  10  to  15  per  cent,  less  when  the  product  treated  is  low  grade 
middlings  (reduction  of  the  offals). 

We  must  say  that  the  works  state  the  capacity  of  their  roller  mills 
with  great  discretion,  allowing  a  reserve  of  20  to  25  per  cent,  sometimes, 
in  comparison  to  the  capacity  attainable  in  practice.  But  we  repeat,  it 
must  be  borne  in  mind,  that  a  capacity  forced  above  the  normal  (some- 
times reaching  35  per  cent.)  is  only  injurious  to  the  work.  Many  cases 
are  known  in  which  the  mills  compelled  the  steam  engine  to  work  with 
an  overload  of  almost  50  per  cent,  without  any  allowance  for  the  steam 
capacity  of  the  boilers. 

Those  mills  ground  30  to  35  per  cent,  over  the  quantity  of  grain  they 
were  calculated  to  reduce,  and  the  millers  considered  themselves  to  be 
the  gainers.  In  their  ignorance,  however,  they  did  not  understand  that 
by  working  with  damp  steam  they  almost  doubled  the  expenses  of  pro- 
duction, not  to  mention  the  fact  that  the  flour  grew  worse,  which  they, 
of  course,  would  never  admit. 

The  above  table  affording  us  no  possibility  of  reckoning  out  the 
capacity  of  the  roller  mills  for  the  various  breaks,  we  must  consult  the 
following  table,  in  which  the  working  length  of  the  rolls  for  different 
grinding  systems  and  successive  breaks  are  given : 

TABLE    XXVII 

LENGTH  OF  ROLLS  FOB  ONE  SACK  OF  STOCK  REDUCED  PER 
TWENTY-FOUR  HOURS 


BREAK. 

I. 

II.              III. 

IV. 

V. 

VI. 

VII. 

VIII. 

High  grinding    . 

a  s 

a  J3 

2-62-3-00 

3-75-4-12  3-75-4-12 

2-62-3-37 

2-62-3-00 

2-25-2-62 

2-25-2-62 

1-88-2-25 

Medium  (semi-j     cj* 
high)  grinding/  ''£  ^ 

3-00-3-15 

4-50-4-62 

4-50-4-62 

3  -00-3  -75^2  -62-3  -00 

2-25-2-62 

Low  grinding 

High  rye  grind-  ) 
ing       .     .     .    f 

Ilebreakor  scratch 

Si 

6-00-7-50 
4-12-5-37 
3-75-412 

4-62-5-25 
4-50-4-62 
337-3-75 

3-37-3-75 
3-12-3-75 
3-00-3-37 

3-37-3-75 
3-00-3-12 
2-40-2-62 

2-62-3-00 

2-47-2-62 

i 

(Smoot 
rolls  1-87 
per  sack 

i  crushing 
-2-25fmi. 

The  data  of  this  table  are  average  quantities  for  Russian  mills  working 
on  hard  and  soft  wheats.  The  smaller  figures  refer  to  the  hard  grain,  the 
greater  to  the  soft. 


308 


FLOUR    MILLING 


[CHAP,  iv 


Baumgartner  offers  the  following    capacity  for    break    and  various 
roller  mills,  which  is  considerably  below  the  data  of  the  works : 

TABLE    XXVIII 

CAPACITY  OF  ROLLER  MILLS  ACCORDING  TO  BAUMGARTNER 
1.  Crushing  Mills  (Quetschstiihle) 


Diameter  of  rolls  in  mm. 

Capacity  for  100  mm.  of  | 
length  in  klg.        .         .  ( 

D  mm. 
Q  klg. 

t  250 
200 

300 
250 

350 
310 

400 
360 

450 

400 

500 
450 

2.  Rolls  for  High  Break,  Hochschrot  (Brechstuhle) 

Z>  =  220  mm.,  Q  =  250  klg.  (one  pair  of  rolls). 
D  =  250  mm.,  Q  =  250  klg.  (three-roller  mill). 

3.  Break  Rolls  (Schrotstiihle) 


Diameter  of  Rolls  —  D  mm. 

220 

250 

300 

350 

400 

450 

Qklg. 

Wheat  —  plain  grinding 

80 

100 

120 

140 

150 

for 

„         semi-high  grinding 

90 

110 

130 

150 

100  mm. 

,,         high  grinding        ... 

125 

140 

165 

of  length. 

Rye  —  plain  grinding  .... 

... 

70 

..85 

95 

105 

4.  Porcelain  Rolls  (Porzellansttihle) 


Diameter  of  Rolls  —  D  mm. 

220 

300 

350 

Q  klg.  for    j  Reduction  of  Coarse  Middlings   . 

25 

45 

65 

100  mm. 

of  length.  J             „              Fine           ->, 

18 

30 

45 

5.  Smooth  Cast-iron  Rolls  (Hartguss-Glattstiihle) 


l_ 

Diameter  of  Rolls  —  D  mm. 

220 

250 

300 

350  1  400 

1 

Q  klg.  for  }  Reduction  of  Coarse  Middlings 
;  I  100  mm. 

45 

55 

70 

85 

100 

-'  of  length.   J            „              Fine            „ 

30 

40 

50 

60 

70 

FLOUR   MILLING 


309 


CHAP.    IV] 

It  is  to  be  regretted  that  Baumgartner  does  not  mention  the  origin 
of  these  tables,  which  raise  some  doubts  in  our  minds.  We  must  re- 
mark, by  the  way,  that  in  modern  practice  rolls  of  such  diameters  as 
450  to  500  mm.  are  not  known. 

By  putting  our  data  in  the  form  of  capacities  to  1  cm.  or  1  inch  for 
the  whole  break  process,  we  obtain  the  following  table  : 


TABLE    XXIX 

CAPACITY  TO  1  CM.  OR  1  INCH  PER  TWENTY-FOUR  HOURS  FOR  THE 
WHOLE  BREAK  PROCESS  IN  LBS. 


Kind  of  Grinding. 

To  1  cm.  of  Length  of 
the  Rolls. 

To  1  inch  of  Length  of 
the  Rolls. 

High  wheat  grinding  .... 

111-55-128-79 

278-87-321-98 

Medium 

5J                         JJ                      .... 

128-62-140-92 

321-62-352-30 

Low 

5)                       »                     .... 

138-27-161-28 

345-63-403-20 

Rebreak 

or  scratch  rolls  . 

Depends  on  the  number  of  rebreaks 

High  rye 

grinding        .... 

120-11-141-12 

300-28-352-80 

If  we  compare  the  capacities  reckoned  out  for  the  first  break  with 
the  factory  data,  we  find  that  our  table  shows  15  to  17  per  cent,  more 
than  is  given  by  the  works.  In  calculating  the  dimensions  of  the  rolls 
it  is  better  to  follow  this  table,  as  its  data  define  a  perfectly  normal 
capacity  of  the  rolls,  without  any  superfluous  reserve  and  without 
injurious  overloading  of  the  machine. 

In  computing  the  capacities  of  rolls  for  high  rye  milling  we  have  kept  in 
mind  the  fact  that  in  the  first  break  the  grain  treated  has  been  previously 
split  down  its  crease,  in  passing  through  smooth  crushing  rolls  the  capacity 
of  which,  as  shown  in  the  table,  is  defined  at  1*87  to  2*25  mm.  to  one  sack 
of  rye  per  twenty-four  hours. 

When  calculating  the  sizes  of  corrugated  rolls,  we  must  bear  it  in  mind 
that  their  capacity  for  one  and  the  same  passage  increases  with  the 
diameter,  remembering  at  the  same  time  that  a  greater  amount  of  power 
is  consumed.  In  selecting  corrugated  rolls  for  high  and  medium  grind- 
ing, the  diameter  of  220  mm.  may  be  decided  upon  if  their  length  does  not 


310  FLOUR   MILLING  [CHAP,  iv 

exceed  1000  mm.  Should  the  capacity  of  the  mill,  however,  require 
rolls  longer  than  1000  mm.,  then  the  diameter  employed  ought  to  be 
250  mm. 

For  low  grinding  rolls  250  to  300  mm.  in  diameter  should  be  used, 
and  300  to  350  mm.  for  single  and  high  rye  grinding. 

Example  of  Calculation. — To  illustrate  clearly  the  use  of  the  table 
for  calculating  the  dimensions  of  the  rolls,  according  to  the  capacity 
given  of  the  mill,  we  shall  take  one  example. 

We  are  required  to  calculate  the  dimensions  of  the  break  rolls  for  a 
wheat  mill  on  a  high  grinding  system  yielding  400  sacks  per  day.  Sup- 
posing the  wheat  <to  be  of  medium  quality  as  regards  hardness,  and  in 
normal  condition,  we  shall  turn  to  the  first  limits  of  the  data  for  high 
grinding. 

For  the  first  break  we  have  :  one  sack  of  product  per  day  is  reduced 
by  2 '62  mm.  of  length  of  the  rolls.  Consequently,  the  dimensions  of  the 
rolls  for  the  first  break  are  : 

2'62  x  400  =  1048  mm. 

The  capacity  for  high  wheat  grinding  in  our  table  being  referred  to 
the  220  mm.  diameter  of  rolls,  we  must  take  a  diameter  of  250  mm. 
since  the  length  of  the  rolls  is  great.  But  then  the  capacity  of  the  mill 
will  increase  according  to  the  factory  data  by  5  to  7  per  cent.  Therefore 
we  may  use  rolls  5  to  7  per  cent,  shorter.  Thus  the  dimension  of  the  rolls 
for  the  first  break  will  be  : 

First  break— 1000  x  250  mm.,  one  pair  of  rolls. 

Second  „  3'75x  400  =  1500  mm. 

Third      „  3'75  x  400  =  1500  mm. 

Fourth   „  2-62x400^1000  mm. 

Fifth       ,,  2'62  x  400~1000  mm. 

Sixth      ,,  2-25  x  400  =  900  mm. 

Seventh  „  2*25  x  400  -  900  mm. 

Eighth    „  1-88  x  400~750  mm. 

Thus  we  have  obtained  three  pairs  of  rolls  at  1000  mm.,  two  pairs  at 
1500  mm.,  two  at  900  mm.  and  one  at  750  mm.  It  being  always  more 
advantageous  to  use  four-roller  mills,  such  a  combination  is  incon- 
venient. For  this  reason,  we  shall  take  a  pair  of  roUs  for  the  sixth  break 
at  1000  mm.  instead  of  900  mm.,  and  for  the  seventh  and  eighth  at  800 
mm.  instead  of  900  and  750  mm.  Such  a  combination  is  advantageous, 
because  without  reducing  to  the  capacity,  we  shall  have  four  mills 
with  two  pairs  of  rolls  each. 


CHAP,  iv]  FLOUR   MILLING 

„    1000  X  250  mm.  —  First   break. 
One  mill  mm  _Fourth 


J  1500  x  250  mm.  —  Second  „ 

1500  x  250  mm.—  Third  „ 
1000  x  250  mm.—  Fifth 
1000  x  250  mm.  —  Sixth 

800  x  220  mm.  —  Seventh  ,, 

800  x  220  mm.—  Eighth  ,  , 

For  the  seventh  and  eighth  breaks,  rolls  of  250  mm.  in  diameter  may 
be  employed.  Then  the  capacity  of  the  seventh  break  will  attain  the 
normal  (according  to  our  calculation),  and  consequently  the  sixth  and 
seventh  breaks  will  have  a  reserve  capacity.  However,  if  possible,  the 
dimensions  of  the  rolls  according  to  the  calculation  should  be  adhered  to. 
This  may  be  done  by  coupling  the  rolls  of  the  break  and  reduction  passages, 
which  depends  on  the  suitable  dimensions  of  the  reduction  rolls.  Accord- 
ing to  our  calculation,  the  fifth  and  eighth  breaks  remain  without  a 
pair.  According  to  the  number  of  kinds  of  meal,  reduction  rolls  having  a 
length  of  1000  mm.  and  750  mm.  may  be  obtained,  and  then  in  one  machine 
both  break  and  reduction  can  be  united.  This  would  be  unavoidable 
if  we  had  (with  the  given  capacity)  seven  breaks  instead  of  eight. 

A  computation  of  the  break  rolls  may  be  likewise  made,  with  the  assist- 
ance of  Table  XXVIII,  where  the  capacity  per  day  to  1  cm.  is  shown. 

Example.  —  Let  us  suppose  the  given  capacity  of  the  mill  per  day  to 
be  400  sacks  of  high  wheat  grinding.  We  are  required  to  calculate  the 
length  of  the  break  rolls,  knowing  the  capacity  to  1  cm.  per  day. 

The  aggregate  length  of  the  break  rolls  we  obtain  in  cms.  by  dividing 
280x400  by  128'79  (or  111'55  Ib.  which  is  the  capacity  per  day  to  1  cm. 
of  the  length  of  the  rolls,  according  to  Table  XXIX,  p.  309)  : 

280  X  400 


The  total  length  obtained  must  now  be  divided  proportionately  to 
the  dimensions  of  each  break  roll  shown  in  Table  XXVII,  p.  307  : 

First  break  —  ^~      =  1050  mm. 


Second     „  -  1500  mm. 

Third 


Eighth     „  -   750mm. 


FLOtJB   MILLING  [CHAP.  IV 

In  this  manner  the  dimensions  of  break  rolls  of  the  other  types  of 
grinding  too,  mentioned  in  Table  XXIX  may  be  calculated. 

We  shall  pass  to  the  definition  of  the  number  and  the  sizes  of  the 
smooth  roUs  after  we  have  become  intimately  acquainted  with  the  grind- 
ings.  At  the  present  moment  we  must  direct  our  attention  to  the 
machinery  finishing  the  work  of  the  roller  mills. 

9.  Brush  Machines 

The  break  process  may  not  be  regarded  as  finished  until  after  the  last 
break  aU  the  bran  is  thoroughly  cleaned  and  the  flour  and  middlings 
adhering  to  the  bran  which  the  grooves  do  not  shear  away  are  separated 
from  it.  An  increased  number  of  breaks  would  give  certain  results  in  this 
respect,  but,  firstly  even  the  eighth  break  yields  no  more  than  1  to  1 J  per 


FIG.  288. 

cent,  of  break  flour,  and  therefore  there  is  little  sense  in  making  the  pro- 
duction dearer  by  adding  another  breaking  passage  ;  secondly,  a  lengthen- 
ing of  the  breaking  passages  results  in  the  reduction  of  the  bran,  which 
lowers  its  value  as  feed.  However,  to  make  "  rich  "  bran,  i.e.  with  the 
mealy  part  of  the  grain  not  separated  from  it,  means  the  loss  of  a  certain 
percentage  of  flour  (up  to  1|  per  cent.).  Since  that  is  the  case,  the  sifted 
bran  should  be  treated  in  a  machine  that  will  separate  away  the  meal 
and  is  not  expensive.  For  this  purpose  brush-machines  are  used. 

The  plainest  type  of  a  brush  machine  which,  with  several  alterations 
in  its  construction,  may  be  employed  for  that  work,  is  described  in 
p.  1 12,  Fig.  102.  A  more  complicated  brush  machine,  but  at  the  same  time 
having  a  greater  capacity,  is  shown  in  Fig.  288.  This  (G.  Daverio's) 
machine  has  a  rotating  drum  A  clothed  with  a  sheet-iron  sieve  (removed 
in  the  drawing)  with  meshes  \  to  J  mm.  in  diameter,  inside  which  there 
rotates  in  the  same  direction  a  drum  with  brush  beaters  B.  The  fibre 


CHAP,  iv]  FLOUR   MILLING 

brushes  on  these  beaters  are  set  in  a  helical  line,  owing  to  which  the  bran 
travels  to  the  outlet  of  the  machine.  The  delivery  to  the  machine  is 
marked  by  the  arrow  8.  The  brush  drum  is  driven  (200  to  240 
revolutions  per  minute)  from  the  belt-pulley  G.  The  belt-pulley  D, 
by  means  of  the  belt-pulley  E,  transmits  the  motion  to  the  worm,  while 
F  with  the  aid  of  the  belt-pulley  G  does  the  same  for  the  drum  with  the 
sieve  (24  to  30  revolutions).  During  operation  the  meal  is  obtained  as 
throughs  and  the  bran  is  tailed  over. 

For  adjusting  the  distance  between  the  casing  of  the  drum  and  the 
brushes,  there  are  the  screws  a,  by  which  the  ribs  with  the  brushes 
are  attached.  These  screws  run  through  the  rim  of  the  pulleys  H  (three 
to  four  pulleys)  fixed  with  keys  to  the  shaft  of  the  brush  drum. 

Daverio's  works,  as  well  as  others,  make  these  machines  with  fixed 
drums.  Sometimes  a  part  of  the  brush  beaters  is  supplanted  by  steel 
ones  spirally  disposed.  The  casing  of  the  working  drum  is  also  clothed 
with  a  wire  sieve. 

The  capacity  of  such  machines  with  a  stationary  casing  is  given  at 
432  to  1080  Ib.  per  hour,  D  (diameter  of  casing)  being  250  mm.  to  720  mm., 
and  L  (length  of  casing)  1000  to  2000  mm.  ;  others,  with  a  rotating 
casing  864  to  2592  Ib.  per  hour,  with  Z>  =  450  to  700  mm.,  and  L  1000  to 
2500  mm. 

10.  Detachers 

In  grinding  the  fine  and  coarse  middlings,  when  it  is  necessary  to 
impart  strong  pressure  to  the  smooth  rolls,  the  crushing  of  a  certain  per- 
centage of  stock  to  flakes  is  inevitable — the  meal  flakes  particularly 
often,  when  the  rolls  are  badly  fed  and  do  not  receive  an  even  sheet  of 
product,  but  narrow  streams,  owing  to  the  damp  product  sticking  to 
the  feed  plates  and  forming  knots.  The  meal  flakes  thus  formed  and 
compressed  fast  may  pass  to  the  sieve  in  that  shape  and  be  removed  as 
overtails,  if  no  steps  are  taken  towards  loosening  them. 

Such  flakes  are  loosened  in  detachers,  which  receive  the  product  on 
its  leaving  the  rolls  and  break  the  flakes  down  to  meal.  There  are  three 
types  of  detachers — brush,  pin,  and  screw  detachers. 

Brush-detacher. — The  ordinary  construction  of  the  brush-detacher  is 
shown  in  Fig.  289.  The  cast-iron  chamber  A  has  a  timber  or  iron  cover 
B  with  an  opening  D  for  the  passage  of  the  product  down  arrow  8.  Inside 
the  chamber,  down  its  whole  length,  there  is  a  fibre  brush  C  running  at 
350  to  1200  revolutions.  The  stock  passes  in  between  the  brush  and  the 
wire  sieve  E,  where  the  meal  flakes  are  reduced  to  flour.  Part  of  the  flour 


314 


FLOUR   MILLING 


[CHAP,  iv 


passes  through  the  sieve  and  part  is  flung  by  the  brush  over  the  sieve  as 
indicated  by  arrows  S^  The  distance  between  the  brush  and  the  sieve 
is  regulated  with  nuts  F  by  means  of  a  simple  link  mechanism.  The  ends 
G  of  the  screws,  passing  through  openings  in  the  frame,  serve  as  guides. 


FIG.  289. 

La/oris  Pin-detacher. — Fig.  290  represents  a  double  pin-detacher  from 
the  French  works  of  F.  Lafon  (Tours).  The  product  moves  as  shown  by 
arrows  8  and  falls  into  conic  sieve  chambers  A.  Here  it  is  caught  up  by 
the  pins  which  break  down  the  flakes.  The  pins  are  fixed  on  the 
hub  (7,  which  is  attached  to  the  axle  B  with  bolts  a.  The  covers  D  are 
cast  in  one  block  with  the  bearings  for  the  journals  of  the  axle. 


FIG,  290, 

The  loosened  product  flows  partly  through  the  sieve  and  partly 
through  the  outlet  down  arrow  8^  The  number  of  revolutions  of  the 
pin  drum  is  1100  to  1750  per  minute.  The  bearings  are  ring-lubricated. 

SecVs  Worm-detacher. —Both  the  brush  and  the  pin-detachers  answer 
their  purpose— that  of  breaking  down  the  flakes.  But  both  again  have 


CHAP.    IV] 


FLOUR   MILLING 


315 


Inlet 


the  defect  that  they  reduce  the  branny  particles,  owing  to  which  the 
offal  cannot  be  separated  off  on  the  dresser  and  give  a  darker  colouring 
to  the  meal.  Besides  that,  Lafon's  detacher,  operating  by  impact,  has  all 
the  defects  of  the  disintegrator  already  discussed. 

These  inconveniences  are  done  away  with  in  the  new  type  of  a  detacher, 
shown  on  Fig.  291.  Its  main  part  is  a  short  worm,  rotating  with  the  velo- 
city of  250  revolutions  per  minute  in  a  cylindric  casing  with  a  small 
dead  space.  This  worm  conveys  the  stock  to  the  outlet  of  the  machine, 
and  the  stock  passes  between  the  valve 
d  and  the  roll  b,  which  are  brought  into 
motion  by  the  belt-pulley  a  with  the  aid 
of  a  worm  gear,  not  shown  in  the  draw- 
ing. The  force  of  pressure  of  the  valve 
upon  the  passage  of  the  stock  is  adjusted 
by  means  of  a  spiral  spring  e  and  a  screw  g. 
For  cleaning  the  roll  there  is  a  scraper  /. 

In  a  detacher  arranged  in  this  manner  the  stock  is  well  stirred  and 
its  particles  are  rigorously  rubbed  against  each  other  in  the  space  between 
the  casing  outlet,  the  valve,  and  the  roll.  The  flakes  are  very  thoroughly 
broken  down,  while  the  mealy  particles  are  but  slightly  reduced  during 
the  operation. 

In  this  way  all  the  flakes  are  triturated,  and  the  particles  of  flour, 
bran,  and  germ  separated  from  the  middlings,  after  which  the  stock 
is  easily  and  very  satisfactorily  dressed. 

Its  compactness  is  another  good  quality  of  this  machine  for  reducing 
flakes  of  meal.  This  detacher  may  be  placed  between  the  roller  mill  and 
the  elevator,  or  between  the  elevator  and  the  bolting  machine. 


Outlet 


FIG.  291. 


CHAPTER   V 

GRADING  THE   PRODUCT  ACCORDING  TO   SIZE 

I 
SIFTING  THE  PRODUCT 

Purpose  of  Sifting. — The  character  of  the  process  of  grain-reduction  and 
its  nature  inevitably  result  in  a  product  of  various  shapes  and  sizes. 

The  break  process  gives  us  particles  of  flour  as  well  as  a  series  of 
middlings  of  various  sizes.     But  this  product  can  only  undergo  a  further 
/  and  final  treatment  after  it  has  been  graded  according  to  size. 

In  fact  the  distance  between  the  working  surfaces  of  the  reduction 
machines,  millstones,  or  roller  mills  at  any  one  period  of  the  operation 
is  quite  definite,  and  calculated  to  yield  a  product  of  a  certain  size.  Con- 
sequently, if  'the  product  is  of  various  sizes,  a  part  of  it,  being  smaller  in 
size  than  the  distance  between  the  working  surfaces,  will  pass  between 
them  untouched.  If,  however,  we  set  the  working  surfaces  at  a  distance 
smaller  than  the  least-sized  particles,  the  large  grains  will  be  too  violently 
broken  down,  reduced  to  flour,  and  will  form  flakes.  Now,  this  is 
injurious  to  the  quality  of  the  flour,  to  say  nothing  of  the  unproductive 
consumption  of  power  incurred  by  the  strong  pressure  of  the  working 
surfaces.  Hence  it  is  clear  that  if  the  work  of  the  reducing  machines 
is  to  be  satisfactory,  after  every  passage  through  the  breaks  or  reduc- 
tions it  is  necessary  for  the  particles  of  the  product  to  be  graded 
according  to  size. 

In  recommending  a  series  of  successive  reduction  machines,  we  had 
the  complex  grinding  systems  in  view,  in  which  the  necessity  of  sifting 
is  clearly  demonstrable.  But  it  is  likewise  evident  that  sifting  is 
just  as  indispensable  in  plain  milling,  in  spite  of  the  grain  being  reduced 
to  meal  in  one  passage  through  the  grinding  machine.  The  fact  is,  that 
however  great  be  the  pressure  of  the  working  surfaces  upon  the  grain, 
the  offals,  being  more  elastic  than  the  kernel,  offer  greater  resistance  to 
breakage,  and  part  of  them  remains  in  the  shape  of  bran.  Sifting  is  also 
i  /necessary  for  extracting  the  bran  from  the  mass  of  meal 

316 


CHAP,  vj  FLOUR    MILLING  317 

Thus,  sifting  is  necessary  (1)  in  the  complex  milling  process,  to  pre- 
pare the  intermediate  products  for  further  treatment,  by  grading  them 
according  to  size  ;  (2)  in  plain  (single)  milling,  to  separate  the  branny 
particles  from  the  flour. 

The  bran  must  be  likewise  sifted  off  from  the  flour  in  the  final  stages 
of  milling  ;  in  the  break  process  at  the  last  break  and  rebreak,  and  in 
the  reduction  process  at  the  final  reduction  of  the  dark  branny  particles 
of  grain. 

Working  Surfaces. — For  grading  the  intermediate  products  of  milling 
and  for  separating  the  bran  from  the  flour,  bolting  surfaces  are  used.  We 
are  already  acquainted  with  the  principle  of  action  of,  these  surfaces, 
having  met  it  in  the  process  of  separating  the  large  and  small  impurities 
from  the  grain,  where  we  saw  that  all  the  sieves  tail  over  the  large  particles 
as  refuse,  while  the  small  particles  are  bolted  through  the  sifting  meshes. 
From  the  same  grain  cleaning  department  we  know  the  shapes  of  the 
sifting  working  surfaces  and  the  character  of  their  motion.  For  grading 
the  reduced  particles  of  grain  we  have  prismatic,  cylindric,  and  flat  sieves, 
similar  to  those  employed  in  machines  for  grain  cleaning. 

But  while  the  working  surfaces  in  the  bolting  machines  for  grain 
consist  of  sieves  of  solid  sheet-iron  plates  or  of  metal  cloths,  owing  to 
the  greater  resistance  these  materials  offer  to  wear,  in  grading  the 
products  of  milling  metal  cloths  are  used  only  for  the  coarser  particles. 
The  rest  of  the  product  in  the  meantime  is  bolted  on  silk  sieves,  though 
many  attempts  are  being  made  at  present  to  substitute  metal  cloth  for  silk. 

If  we  take  home  manufacture  into  consideration,  then  the  hair-cloth 
(mostly  horse-hair)  used  for  sieves  for  home  sifting  should  be  mentioned. 
We  may  say  that  the  hair-cloth,  used  from  the  remotest  time  for  sifting, 
is  better  than  silk  or  wire,  as  it  is  hydroscopic  and  consequently  never 
swells  or  grows  rusty.  Further,  it  is  sufficiently  strong  to  stand  a 
long  period  of  work.  But  the  uneven  size  of  the  hairs,  their  unequal 
diameter  and  length,  does  not  allow  this  material  to  be  used  for  factory- 
made  sieves. 

It  was  comparatively  but  a  short  time  ago  that  woollen  cloth  of  comb- 
yarn  was  largely  used  on  plain  short  system  mills  owing  to  its  cheapness. 
But  the  nappiness  of  the  woollen  threads  rendered  the  sifting  imperfect, 
reducing  the  quality  and  the  quantity  of  the  work. 

Metal  Cloths. — As  regards  solidity  and  durability,  metal  sieves  are 
the  best.  But  their  essential  defect  is  the  liability  to  rust,  which  very 
rapidly  destroys  the  sieves  working  in  unfavourable,  that  is  damp, 
conditions. 


318  FLOUR   MILLING  [CHAP,  v 

We  must  admit,  however,  that  this  defect  only  refers  to  iron  sieves. 
Steel  is  more  rust-resistant,  while  phosphor-bronze  cloths  excel  even 
steel  in  that  respect.  Besides  iron,  steel,  and  bronze,  the  wire  of 
the  bolting  surface  is  also  made  of  pure  copper.  But  copper  sieves 
cannot  be  recommended,  because  that  metal  gives  a  poisonous  oxide 
when  the  sieve  works  in  damp  air. 

Though  metal  sieves  for  bolting  fine  middlings  and  meal  have  already 
made  their  appearance  on  the  market,  they  have  not  found  their  way 
into  the  ranks  of  the  machines  generally  used  in  mills,  being  very 
expensive. 

When  it  is  desired  to  employ  metal  sieves  for  bolting  fine  middlings 
and  flour,  phosphor-bronze  cloths  or  of  other  rust -resistant  copper  com- 
binations should  be  taken.  In  using  metal  sieves  we  must  remember 
that,  owing  to  the  high  heat -conductivity,  the  moisture  from  the  raw 
product  precipitates  upon  the  metal  sieve  (the  dew  phenomenon),  which 
is  dangerous,  for  the  reason  that  the  moistened  parts  of  the  sieve  im- 
mediately become  blinded  with  starchy  paste  and  the  sifting  will  stop. 
For  this  reason  bolting  machines  with  metal  sieves  should  be  subjected 
to  an  energetic  exhaust. 

Silk  Sieves. — A  tissue  of  white  or  yellow  raw  silk,  comparatively  cheap, 
durable,  and  scarcely  at  all  hygroscopic,  is  very  successfully  adopted, 
where  metal  sieves  cannot  be  employed. 

Good  silk  cloths,  prepared  of  pure  silk  threads,  are  designated  by 
the  kind  of  their  interlacing  and  also,  like  those  of  metal,  by  numbers,  for 
products  of  different  sizes.  In  making  the  choice  of  the  cloth  particular 
attention  should  be  paid  to  the  purity  of  the  silk.  Being  an  expensive 
material,  it  is  often  adulterated.  Owing  to  finishing,  silk  of  low  quality 
often  becomes  firm,  smooth,  and  glossy,  i.e.  possesses  in  its  outward 
appearance  all  the  good  qualities  of  sterling  cloth.  In  such  a  case  even 
an  experienced  eye  will  not  be  able  to  distinguish  it  from  good  stuff. 
Finished  silk,  however,  is  very  hygroscopic,  and  swells  after  absorbing 
a  small  quantity  of  moisture  on  being  held  a  short  time  between  slightly 
dampened  fingers.  This  silk  absorbs  the  moisture  of  the  evaporating 
product,  swells,  and  causes  the  meshes  of  the  tissue  to  contract.  The 
flour,  turning  to  paste  on  the  damp  sieve,  blinds  it  in  the  end  and  it  stops 
working. 

The  finishing  of  bad  silk,1  i.e.  imparting  to  its  threads  the  firmness  and 
glossiness  of  good  material,  is  done  chiefly  by  means  of  starch  (coarse 
adulteration)  and  by  means  of  Arabian  resin  (a  finer  adulteration).  The 

1  Pr,  P.  Hermann,  Colaric  Textile  Chemical  Analysis, 


FLOUR   MILLING 


319 


CHAP,  v] 

adulteration  of  the  silk  may  be  detected  by  immersing  the  sample  to 
be  tested  into  pure  or  an  80  per  cent,  solution  of  alcohol,  shaking  it  two 
or  three  minutes  (half  a  glass  of  alcohol  solution  and  a  sample  of  one- 
sixteenth  of  a  foolscap  may  be  taken),  and  then  letting  the  solution  settle 
for  a  half  to  three-quarters  of  an  hour.  If  the  silk  is  finished  with  starch, 
then  a  white,  loose  sediment  will  remain  in  the  glass  ;  if  resin  has  been 
used  for  finishing  we  obtain  a  white  turbidness,  white  flakes,  or  a  white 
gelatinous  sediment,  according  to  the  quantity  of  finishing  stuff. 
*  The  silk  sieves  have  two  kinds  of  texture  of  their  threads,  linen  and 
gauze  texture.  The  linen  texture  shown  on  Fig.  292  is  an  ordinary  cloth 
with  the  threads  of  the  warp  a  and  the  woof  b  lying  crosswise.  The 
gauze  texture  (Fig.  293)  differs  from  the  linen  in  that  its  warp  consists 
of  two  threads,  a  and  6,  one  of  them  passing  under  the  woof  c,  the  other 
over  it.  In  between  the  warps  those  threads  cross  each  other. 

The  gauze  bolting  cloth  is 
stronger  and  more  durable  as 
regards  the  even  size  of  the 
sieve  meshes  (during  cleaning, 
or  in  mounting).  But  the  me.shes 
of  the  gauze  tissues  are  less 
regular  than  in  the  cloth  of  the 
linen  texture. 

To   make   the    shape    of    the 

meshes  in  the  linen  texture  cloths  more  stable,  threads  of  greater 
thickness  used  to  be  woven  into  the  tissue  1J  to  2  cm.  distant  from 
each  other,  to  impart  more  firmness  to  the  cloth.  But  this  was  of  little 
use,  as  at  the  same  time  it  reduced  the  useful  working  area  of  the 
cloth,  and  made  the  cloth  more  expensive.  These  attempts  were  dis- 
continued some  twenty  years  ago,  but  now  they  seem  already  to  be 
forgotten,  and  such  cloths  have  again  appeared  on  the  market.1 

Modern  technics  of  cloth  manufacture  produce  a  quite  satisfactory 
silk  tissue  of  linen  texture,  which  very  firmly  resists  displacement  of  the 
meshes,  even  when  cleaned  with  a  brush.  It  is  only  necessary  to  use  the 
material  of  good  factories,  and  beware  of  adulterated  silk.  A  good  silk 
cloth  serves  for  three  (on  coarse  and  sharp  stock)  to  six  years  (on  fine 
and  soft  stock). 

In  choosing  the  cloth — metal  or  silk — one  should  see  that  the  threads 

1  The  "  Carre  "  cloths.  The  wear-resistancy  depends  not  on  the  increase  in  weight  or  the 
solidity  of  the  sieve  caused  by  the  thick  threads,  but  on  the  standard  quality  of  all  the 
threads, 


FIG.  292. 


FIG.  293. 


320  FLOUR    MILLING  [CHAP,  v 

are  of  equal  thickness  and  the  meshes  of  equal  dimensions.     Only  such  a 
sieve  gives  throughs  or  overtails  equal  in  size. 

Any  rough  unevenness  of  the  threads  and  an  irregular  yarn  strike  one 
on  the  most  superficial  examination  of  the  cloth.  But  a  somewhat 
inferior  tissue  may  be  told  from  good  stuff  only  with  the  assistance  of  a 
particular  kind  of  lense  shown  on  Fig.  294. 

This  lense  consists  of  two  metal  plates  A  and  B  folding  up  on  a  third 
plate,  the  stand  C.  The  plate  A  has  a  square  hole  in  it  of  J  to  1  inch,  in 
the  plate  B  the  lens  L  is  set.  Before  inspecting  the  cloth  it  is  laid  on 
smooth  black  or  dark  paper,  and  then  the  lense  is  placed  as  shown  in  the 
drawing.  In  examining  through  the  lense  the  square  piece  of  the  cloth 
framed  in  the  square  hole  through  the  plate  A ,  it  is  easy  to  notice  the  regu- 
larity or  irregularity  of  the 
threads  and  the  meshes,  and  to 
count  them  to  test  the  number 
of  the  cloth.  To  examine  the 
silk  more  accurately  it  must 
be  inspected  through  the  lens 
in  several  places. 

Numeration  of  the  Cloths. — 
With  the  numeration    of   the 
metal   sieves   we    become    ac- 
quainted in  the  part  treating 
FJQ.  294.  °f  grain-cleaning.      As  regards 

the  numeration  of  silk  cloths, 
here  we  also  have  no  definite  fixed  international  standard. 

Silk  being  used  for  sifting  flour  and  grading  the  coarse  and  fine 
middlings  according  to  size,  numeration  has  been  correspondingly 
established  for  the  flour  and  the  middlings  cloths  separately.  In  addi- 
tion there  is  the  Swiss  and  the  French  numeration  of  the  cloths  of  both 
kinds.  Further,  the  numeration  of  the  flour-cloths  differs  from  that  of 
the  middlings  cloths.  Almost  all  European  works  (except  the  French) 
have  accepted  the  Zurich  numeration  of  flour  silks,  and  the  Swiss  for 
middlings  ;  the  same  numeration  is  accepted  in  America,  where  the 
American  Bolting  Cloth  Co.  in  St.  Louis  is  considered  to  be  the  best 
factory. 

The  quality  of  the  silks  considerably  influences  their  numeration, 
which  explains  why  a  different  numeration  has  been  adopted  for  middlings, 
a  coarser  product  requiring  a  stronger  tissue.  In  respect  to  their  strength 
the  cloths  are  divided  into  five  kinds  ; 


CHAP.    V] 


FLOUR   MILLING 


321 


for  reels. 


and  centrif       ls< 


(1)  Plain  cloths  (Prima) 

(2)  Heavy  cloths  (Extra)      .          .  f 

(3)  Double  heavy  (Double  Extra).  )  * 

(4)  Treble  heavy  (Triple  Extra)    .  J 

(5)  Middlings  cloths  (Gazes  a  Gruaux). 

Of  these  five  kinds  of  cloths  those  for  middlings  are  the  most  dense 
(thicker  threads). 

The  plain  cloths  (Prima)  have  the  numbers  :  0000,  000,  00,  0,  1,  2,  3 
up  to  20,  and  at  the  American  factories  up  to  No.  25.  In  most  cases, 
however,  cloths  over  No.  17  are  not  manufactured. 

Before  passing  on  to  the  further  characteristics  and  comparison  of 
silks,  we  give  the  numeration,  number  of  threads,  the  number  and  size 
of  the  meshes  in  the  Prima  sieves  (Swiss  silks). 


TABLE    XXX 


Silk  No. 

Number 
of  Threads 
to  1  cm. 

Number  of 
Meshes  to 
1  square  cm. 

Dimensions  in 
mm.  of  each  side 
of  the  Meshes. 

Silk  No. 

Number 
of  Threads 
to  1  cm. 

Number  of 
Meshes  to 
1  square  cm. 

Dimensions  in 
mm.  of  each  side 
of  the  Meshes. 

0000 

7 

49 

1-43 

9 

38J 

1470 

0-26 

000 

9 

81 

l;li 

10 

43 

1844 

0-23 

00 

Hi 

133 

0-87 

11 

46 

2079 

0-22 

0 

15 

222 

0-67 

12 

49J 

2436 

0-20 

1 

19 

369 

0-53 

13 

51 

2591 

0-19 

2 

21| 

460 

0-46 

14 

55 

2996 

0-18 

3 

23 

529 

0-43 

15 

59 

3481 

0-17 

4 

24i 

602 

0-41 

16 

62 

3844 

0-16 

5 

26 

680 

0-38 

17 

64 

4096 

0-153 

6 

29. 

848 

0-35 

18 

66 

4290 

0-151 

7 

32 

1037 

0-31 

19 

67 

4422 

0-149 

8 

34 

1136 

0-29 

20 

68 

4624 

0-145 

Of  these  cloths  Nos.  0000  to  4  give  large  and  small  middlings  as 
throughs,  Nos.  5  to  7  dunst  or  coarse  flour,  while  Nos.  8  to  20  give 
finished  flour.  In  practice,  however,  the  number  of  silk  numbers  is 
considerably  limited,  as  we  shall  see  when  studying  the  diagrams  of 
mills. 

The  heavy  cloths  (Extra)  are  manufactured  for  fine  middlings  and  flour, 
and  have  twelve  numbers  from  6  to  17  inclusively. 

The  cloths  of  double  density  (Double  Extra)  have  three  numbers  less 
than  the  Prima,  from  No.  0000  to  No.  17. 

x 


322 


FLOUR   MILLING 


[CHAP,  v 


The  triple  heavy  silks  (Triple  Extra)  like  those  of  the  double,  are 
used  only  for  fine  middlings  and  flour,  from  No.  7  to  No.  15. 

When  denoting  these  four  types  of  cloth,  they  are  marked  in  the 
following  manner  (we  take  the  flour  silk  No.  12  for  example)  : 

Prima — 12. 
Extra— 12  X. 
Double  Extra— 12  XX. 
Triple  Extra— 12  XXX. 

With  these  crosses  the  corresponding  silks  should  be  marked  in  draw- 
ing the  milling  diagrams.  .  < 

The  middlings  sieves,  applied  in  purifiers,  in  the  Swiss  numeration 
are  characterised  in  the  following  table  ; 


TABLE    XXXI 


Number 

Number  of 

Dimensions  in 

Number 

Number  of       Dimensions  in 

Cloth  No. 

of  Threads 

Meshes  to 

mm.  of  each  side 

Cloth  No. 

of  Threads 

Meshes  to      mm.  of  each  side 

to  1  cm. 

1  square  cm. 

of  the  Meshes. 

to  1  cm. 

1  square  cm.      of  the  Meshes. 

14 

51 

28 

•82 

44 

17 

285              0-59 

16 

6 

37 

•66 

46 

174 

308             0-67 

18 

7 

48 

•43 

48 

18J 

339             0-55 

20 

74 

58 

•33 

50 

19 

369              0-52 

22 

84 

71 

•18 

52 

20 

398              0-50 

24 

9 

82 

Ml 

54 

21 

429              0-48 

26 

10 

99 

1-00 

56 

214 

460              0-46 

28 

11 

116 

0-90 

58 

221 

498              0-44 

30 

Hi 

132 

0-87 

60 

23 

529              0-43 

32 

12 

150 

0-83 

62 

24 

565              0-42 

34 

13 

171 

0-77 

64 

24J 

602              0-41 

36 

14 

190 

0-71 

66 

25J 

640              0-39 

38 

144 

213 

0-61 

68 

26 

680              0-38 

40 

154 

239 

0-64 

70 

27 

720             0-37 

42 

16 

258 

0-61 

72 

28 

804              0-36 

In  their  density  the  middlings  sieves  correspond  to  the  Triple  Extra. 
For  grading  the  middlings  cloths  from  Table  XXXI  should  be  em- 
ployed,  because  the  sharp  product  wears  out  the  lighter  cloths  more 
rapidly.  But  sometimes  the  use  of  the  Prima  cloths  (Table  XXX) 
is  preferable;  because  they  are  cheaper.  For  this  reason  we  give  the 
table  of  parallel  numbers  of  the  Prima  and  the  middlings  cloths 
(Table  XXXII). 


CHAP.    V] 


FLOUR   MILLING 
TABLE   XXXII 


323 


Prinia           Middlings 
Nos.                 Nos. 

Prima 
Nos. 

Middlings 

Nos. 

Prima 

Nos. 

Middlings 

Nos. 

Prima 

Nos. 

Middlings 
Nos. 

14 

16 

30 

1 

42 
44 

3 

56 

58 

0000            18 

32 

46 

4 

60 

20 

34 

48 

62 

22 

36 

2 

50 

5 

64 

00 

24 

38 

52 

66 

26 

0 

40 

•• 

54 

7 

68 

The  French  sieves  are  mostly  prepared  of  linen  texture,  and  their 
numeration  is  totally  different  to  the  generally  accepted  Swiss  numeration. 

The  next  table  gives  an  approximate  comparison  of  these  two  numera- 
tions (Table  XXXIII)  with  the  Prima  cloths. 

TABLE    XXXIII 


Prima  Nos. 

French  Nos. 

Prima  Nos. 

French  Nos. 

0000 

20 

7 

95 

000 

15 

8 

100 

00 

30 

9 

110 

0 

40 

10 

120 

1 

50 

11 

130 

2 

60 

12 

140 

3 

65 

13 

150 

4 

70 

14 

170 

5 

80 

15 

180 

6 

90 

16 

200 

324 


FLOUR   MILLING 


[CHAP,  v 


Characteristics  of  the  Intermediate  Products  and  Flour. — Before  con- 
sidering flowsheets  for  the  grading  and  flour  dressing,  it  is  necessary  to 
settle  the  question  of  the  terms  applied  to  the  intermediate  products  in 
connection  with  the  above  numeration  of  sieves. 

The  largest  break  product  is  obtained  from  the  preliminary  break 
(Hochschrot),  when  the  grain  is  broken  in  two  down  the  crease.  If  the 
broken  grain  is  to  tail  over  the  scalper,  sieves  from  No.  8  to  No.  24, 
according  to  the  size  of  the  grain,  must  be  employed.  Then  come  the 
ordinary  breaks  from  6  to  9  in  number.  For  high  break  as  well  as  for 
the  successive  break  passages  we  use  wire  sieves  with  meshes  numbered 
per  inch,  which  were  spoken  of  on  p.  322. 

The  largest  product  in  the  break  process  is  called  semolina,  and  since 
this  semolina  is  sharp  and  rough,  it  is  necessary  to  use  wire  sieves,  which 
are  more  durable. 

After  each  successive  passage  of  the  break  stock  through  the  grinding 
rolls,  its  size  diminishes,  and  reckoning  the  numeration  of  the  wire  sieves 
to  an  inch,  sieves  with  Nos.  from  14  to  40  should  be  used  for  the  last 
break.  The  dimensions  of  the  break  semolina  may  be  reckoned  at  1'4 
mm.  to  0'7  mm.  and  less. 

Further,  we  have  the  rebreak  semolina,  for  sizing  which  wire  sieves 
are  also  required,  Nos.  20  to  40.  The  dimensions  of  the  rebreak  semolina 
are  defined  at  1'35  mm.  and  less. 

The  product  following  in  size  is  the  middlings  of  various  dimensions. 
Generally  up  to  six  numbers  of  middlings  are  distinguished.  To  obtain 
these  middlings  as  overtails,  silk  cloths  are  used  of  the  following  numbers, 
according  to  the  middlings  numeration  in  Table  XXXI. 


TABLE    XXXIV 

NUMBERS  OF  MIDDLINGS  AND  THEIR  CORRESPONDING  SIEVES 


Middlings 

*„, 

Middlings  Cloth 

Nos. 

Prima  Silk                Dimensions  of 
Nos.                  Middlings  in  mm. 

I 

20-24 

0000-00            1-33-1  -11 

2 

24-32 

00-0 

1-11-0-83 

3 

32-40                  0-1 

0-83-0-64 

4 

40-48 

1-2 

0-64-0-54 

5 

48-56 

2-3 

0-54-0-46 

6 

56-60 

3—4 

0-46-0-37 

CHAP,  v]  FLOUR    MILLING  325 

In  giving  the  dimensions  of  the  middlings  in  mm.,  we  understand  this 
to  be  their  largest  measurement  or  diameter,  supposing  them  to  be  of  a 
spherical  shape. 

After  the  middlings  the  product  next  in  size  is  named  "dunst." 
This  product,  dressing  through  grit  gauze  Nos.  60  to  68,  is  tailed  over  on 
Nos.  5  to  7  (Prima  numbers). 

Lastly,  the  granular  flour  is  obtained  as  throughs  from  sieves  Nos.  5 
to  7  and  the  finished  flour  from  Nos.  8  to  13.1 

Diagrams  of  Bolting.—  We  are  already  acquainted  with  the  general 
outline  of  the  operation  of  the  graders  ;  we  have  now  to  study  it  more 

in  detail. 

In  examining  the  process  of  sifting  and  grading  the  break  stock,  we 
notice  three  methods  of  sifting  : 

(1)  The  overtails   are  of   uniform   size,  while   the   throughs  are  of 

various  sizes. 

(2)  The  throughs  are  uniform  in  size,  the  overtails  different. 

(3)  The  overtails  and  the  throughs  are  both  of  various  sizes. 


Dunst 

No.  2.          No.  3.  No.  4.        No.  5.  No.  6. 

FIG.  295. 

For  grading  by  the  first  method,  a  sieve  is  chosen  with  meshes  of  a 
size  which  allows  only  the  largest  product  to  be  tailed  over. 

In  the  second,  the  dimensions  of  the  meshes  allow  only  the  smallest 
product  to  dress  through  the  sieve. 

For  the  third  method,  meshes  suiting  the  medium  of  the  intermediate 
products  are  selected. 

The  application  of  the  third  method  is  expedient  when  it  is  desired  to 
divide  the  work  of  one  sieve  among  several.  In  most  cases  the  second 
and  third  methods  of  sifting  are  adopted. 

Supposing  we  are  required  to  grade  middlings  into  sizes  from  Nos.  2 
to  6  according  to  Table  XXXIV.  Then  we  must  use  sieves  from  Nos.  28 
to  60.  The  first  system  (Fig.  295)  overtails  the  middlings,  the  second 
(Fig.  296)  dresses  them  through.  The  first  system  yields  the  largest 
middlings  No.  2  as  overtails,  and  the  rest  as  throughs.  To  separate  the 
middlings  No.  3,  next  in  size,  a  finer  sieve  has  to  be  used  —  No.  34,  &c.  In 
this  way  the  numbers  of  the  sieves  decrease  until  we  obtain  as  overtails 

1  In  modern  English  mills  the  lowest  flour  silk  number  is  usually  No.  9,  while  in  large 
modern  mills  throughs  of  Nos.  9  and  10  and  even  11  are  sometimes  treated  as  dunst  and 
further  purified  and  reduced  on  the  smooth  rolls. 


326  FLOUR   MILLING  [CHAP,  v 

the  finest  middlings,  No.  6,  and  dunst,  as  throughs.  To  perform  the  work 
in  accordance  with  this  diagram,  the  sieves  have  to  be  disposed  one  below 
the  other.  We  have  already  met  with  such  a  construction  of  sieves, 
when  studying  the  construction  of  grain -cleaning  machines. 

If  employing  the  throughs  system,  we  dispose  the  sieves  in  an  order 
starting  with  the  finer  and  ending  with  the  coarser.  The  first  product 
yielded  as  throughs  by  No.  56  corresponds  to  the  finest  middlings,  the 
second  larger  ones,  &c.  In  the  second  diagram  the  sieves  are  placed  in 
one  plane  or  some  other  form  of  surface.  This  type  of  machine  we  also 
met  in  the  grain -cleaning  section  ;  namely,  the  reel-separator. 

A  comparison  of  these  two  diagrams  leads  us  to  prefer  the  first,  in 
which  there  is  little  product  tailed  over  in  comparison  with  the  general 
mass,  and  consequently  each  sieve  will  be  but  slightly  worn.  In  the 


Break 
middlings 


Y Y Y^ YV T Y Y V 


No.  6.      No.  5.          No.  4.  No.  3.  No.  2.     No.  1. 

FIG.  296. 

second  diagram,  in  which  the  quantity  of  the  throughs  is  small,  the  whole 
mass  of  product  travels  over  the  sieve,  therefore  the  force  of  friction  is 
much  greater  than  in  the  first  case,  and  the  cloth  wears  more  rapidly. 

It  is  best  to  combine  both  these  diagrams  so  as  to  separate  the  coarser 
product  by  the  overtails  system,  and  grade  the  finer  product  by  the 
throughs  system. 

II 

RELATIVE  POSITION  or  THE  SIEVES 

Having  become  acquainted  with  the  grading  diagrams,  we  shall  now 
proceed  to  work  out  the  relative  position  of  the  sieves. 

We  have  the  following  diagrams  of  the  disposition  of  sieves  according 
to  the  system  of  grinding  : 

(1)  A  diagram  of  the  disposition  of  sieves  for  sifting  the  product  of 

plain  (single)  grinding. 

(2)  Diagrams  for  high  grinding. 

(3)  Diagrams  for  rebreak. 

(4)  Diagrams  for  semi-high  grinding. 

(5)  Diagrams  for  sifting  the  products  of  reduction  of  middlings  and 

dunst. 

The  second  and  the  third  diagrams  for  sifting  the  products  of  high 


CHAP,  v]  FLOUR   MILLING  327 

grinding  consist  of  diagrams  for  the  break  and  rebreak  products,  the  re- 
duction of  middlings,  and  grinding  of  the  low  grade  stock.  In  addition  the 
diagrams  of  sifting  for  the  high  and  the  semi-high  rye  grinding  likewise 
belong  to  this  category. 

(1)  Diagram  of  Sieves  for  Plain  Grinding. — The  plain  or  single  grind- 
ing completely  reduces  the  grain  to  flour  at  one  passage,  excepting  an 
insignificant  quantity  of  offals,  which,  owing  to  their  elasticity,  remain 
in  the  shape  of  fine  soft  bran.  The  product  obtained  is  soft,  and  there- 
fore the  sifting  may  be  performed  by  the  second  system,  i.e.  by  throughs, 
without  danger  of  the  sieves  wearing.  Fig.  297  represents  an  arrange- 
ment of  covers  for  plain  grinding.  Experience  has  shown  that  the  more 
product  there  is  on  the  sieve,  the  coarser  should  the  sieve  be  to  yield  as 
throughs  a  product  equal  in  size  to  the  throughs  obtained  when  the  sieve 
is  less  loaded.  Therefore  the  first  sieve  we  use  is  No.  10  or  No.  11,  while 
the  second  and  third  is  one  number  higher,  so  that  the  flour  from  the 
first,  second,  and  third  sieves  should  be  of  an  equal  size.  In  this  way  the 


Nos.  10-11 

Nos.  11-12 

Nos.  11-12 

Nos.  5-6 

Nos.  0-1 

^                       1                       ^ 

Throughs— Flour.  Dunst.  Middlings. 

FIG.  297. 

first  three  sieves  give  flour  as  throughs ;  the  fourth,  dunst ;  the  fifth, 
middlings ;  and  the  bran  is  tailed  over  as  refuse. 

(2)  Diagram  of  Sieves  for  the  Long  System  Break  Process. — The  break 
process  is  performed,  as  we  already  know,  in  such  a  manner  as  to  obtain 
as  much  middlings  and  as  little  break  flour  as  possible.  But  some 
break  flour  is  inevitable,  and  therefore  the  sifting  diagram  contains  sieves 
for  middlings  of  different  numbers  and  flour  sieves. 

On  Fig.  298  may  be  seen  the  diagram  2  for  the  first  break.  This 
diagram  is  a  combination  of  the  first  and  the  second  systems  of  sifting, 
i.e.  the  work  is  done  by  overtailing  and  by  bolting.  The  product,  first 
break,  passes  along  the  arrow  A  to  the  wire  sieve  No.  18  or  No.  20  (we 
give  the  numbers  of  the  wire  sieves  everywhere  to  an  inch).  From  the  over- 
tails  we  obtain  the  first  break  semolina,  while  the  throughs,  the  remaining 
product,  run  to  the  second  wire  sieve,  Nos.  20  to  22.  This  sieve  supple- 
ments the  work  of  the  primary  grader,  as  this  could  not  have  taken  out 
the  whole  of  the  break  semolina.  Therefore  this  sieve  likewise  overtails 
break  semolina.  The  next  is  a  silk  middlings  sieve,  Nos.  34  to  33.  The 
overtails  of  this  sieve  are  the  mixed  middlings,  Nos.  1  to  3,  and  the  throughs 


328 


FLOUR   MILLING 


[CHAP,  v 


likewise  consist  of  a  mixed  product — fine  middlings,  dunst,  and  flour. 
The  duty  of  this  sieve,  which  gives  no  uniform  product,  neither  as  overtails 
nor  as  throughs,  is  to  facilitate  the  work  of  the  more  tender  flour  silks, 
the  fourth  and  the  fifth,  by 'separating  the  coarse  product  (middlings 
Nos.  1  to  3).  The  mixed  middlings  overtailed  on  the  third  sieve 
may  be  subjected  to  a  further  grading  if  necessary  ;  the  throughs  from 

it,  in  the  meantime,  pass  to  the  fourth 
_A    sieve,  which  bolts  the  flour.  Theover- 
1       tails  of  the  fourth  sieve  go  to  the 
fifth,  and  the  throughs  are  again  flour, 
which  mixes  with  the  flour  from  the 
fourth  sieve.     Lastly,  the  sixth  sieve 
gives  fine  middlings  Nos.  4  to  6  as 
overtails,  and  the  dunsts  as  throughs. 
3  Thus,  the   sieves    1   and  2   give 

overtails,  sieve  3  separates  the  pro- 
duct for  further  grading,  sieves  4 
and  5  give  throughs,  and  the  last, 
the  sixth  sieve,  yields  the  graded 
product  as  tails  and  as  throughs. 

The   sixth   sieve   could   be,   and 
sometimes  is,  placed  after  the  third. 
5      Then  the  first  four  sieves  would  be 
operating  on  the  "overtail  system," 
and  the  last  two  giving  throughs,  the 
last  sieve   yielding  dunst    as    tails, 
g      But  the  first  plan   of  disposition  is 

preferable,    for    the    flour    on    the 

Dunst.  fourth  and  fifth  sieves  will  be  sifted 

FIG.  298.  better    if    they    are    more    heavily 

loaded  with  product. 

For  a  shorter  break  system,  for  instance,  with  six  breaks,  this  dia- 
gram may  be  altered  so  that  by  placing  instead  of  the  second  wire  sieve 
the  middlings  sieve  No.  24,  we  obtain  middlings  No.  1.  Then  the  third 
sieve  will  yield  middlings  Nos.  2  to  3,  which  may  remain  unseparated. 
The  other  sieves  can  be  left  in  their  places. 

In  the  diagram  reviewed  there  is  no  sieve  which  would  yield  rebreak 
semolina.  To  obtain  it,  the  second  sieve,  Nos.  20  to  22,  may  be  sub- 
stituted by  a  wire  sieve,  Nos.  24  to  26,  which  gives  the  rebreak 

The  greatest  quantity  of  middlings  (amounting  to  60  per  cent  of  the 


«v- 

*z- 
•5- 

Nos.  18-20 

<- 

I 

«- 

Nos.  20-22 

1 

<- 

Nos.  34-36 

I 

- 

Nos.  11-12 

1 

i 

<- 

«- 

Nos.  12-13 

<- 

<- 

Nos.  58-60 

CHAP.   V] 


FLOUR   MILLING 


329 


bulk  of  grist)  in  an  eightfold  break  is  obtained  at  the  second,  third,  and 
fourth  breaks,  which  induces  us  to  examine  the  diagram  of  position  of  the 
sieves  of,  for  example,  the  third  break,  the  most  characteristic  one,  as  it 
yields  up  to  24  per  cent,  of  middlings.  This  diagram  is  shown  on  Fig.  299. 
The  first  wire  sieve  overtails  break  semolina  ;  the  second  and  third, 
silk  cloths,  yield  coarse  and  medium  middlings,  Nos.  1  to  4.  The  fourth 


Break 
Semolina  <^~~ 


Nos.  25-24 


< B 

1 


Semolina 
Nos.  1-2  ' 


Semolina . 
Nos.  3-4 


Nos.  24-32 


Coarse . 
Bran. 


Dark 
Middlings  <- 

Nos.  4-5. 


Nos.  36-40 


Nos.  40-56 


Nos.  34-40 


Nos.  11-12 


Flour  4 


Semolina 
Nos.  5-6 


<- 

- 

Nos.  11-12 

1 

«- 

<- 

Nos.  12-23 

|                     * 

1 

- 

<- 

Nos.  58-60 

Dunst. 

Dark 
Flour/ 


Nos.  12-13 


Nos. 

12-13 

Dark 
Middlings  ^_ 
No.  6. 


Nos. 

60-63 

FIG.  299. 


I 
Dark  Dunst. 

FIG.  300. 


and  fifth  sieves  yield  flour,  while  the  sixth  sieve  bolts  the  dunst  and  tails 
over  the  fine  middlings,  Nos.  5  to  6. 

Commencing  with  the  fifth  break  the  size  of  the  middlings  diminishes, 
and  at  the  fifth  break  there  is  scarcely  any  middlings  Nos.  1  to  2.  For 
this  reason  the  numbers  of  the  middlings  sieves  increase,  and  some  of  these 
sieves  may  be  discarded  and  flour  or  dunst  numbers  set  in  their  places. 

The  last  break,  which  yields  bran,  dark  middlings,  dunst,  and  flour, 
is  also  characteristic.  For  the  eighth  break  the  diagram  of  sieves  shown 
on  Fig.  300  should  be  adopted. 


330  FLOUR   MILLING  [CHAP.  V 

According  to  this  diagram  the  sieves  1  and  2  yield  overtails,  the 
sieves  3,  4,  and  5  throughs,  and  sieve  6  both  overtails  and  throughs. 

The  tails  from  the  first  wire  sieve,  the  bran,  are  conveyed  to  the  brush 
machine  to  remove  the  mealy  particles  remaining  on  them.  The 
tails  from  the  second  silk  sieve,  the  soft  dark  middlings,  are  sent 
for  reduction.  The  throughs  from  the  third,  fourth  and  fifth  sieves, 
lowest  grade  of  flour,  and,  lastly,  the  throughs  and  the  tails  from  the 
sixth  sieve,  dark  dunst  and  small  dark  middlings,  are  likewise  conveyed 
for  reduction  and  reduced  to  low-grade  flour. 

(3)  Diagrams  of  Sieves  for  Rebreak. — The   number  of  rebreaks  em- 
ployed in  the  Russian  mills  varies  between  1  and  5.     In  the  last  case 
the  rebreak  may  be  regarded  as  a  parallel  break,  and  the  diagram  of 
disposition  of  the  sieves  here  scarcely  differs  from  the  diagrams  for  the 
shorter  (semi-high)  break  process.    But  generally  1  to  3  rebreak  or  scratch 
rolls  are  used.     For  the  rebreaks  the  diagrams  of  the  sieves,  in  their  general 
outline,  are  the  same  as  those  for  breaking,  with  the  sole  difference  that 
the  numbers  of  the  wire  and  the  middlings  sieves  are  higher,  the  product 
being  finer. 

(4)  Diagram  of  Sieves  for  Medium  Break  Systems . — There  is  no  essential 
difference  in  the  diagrams  of  disposition  of  the  sieves  in  the  long  and  the 
medium  systems ;   they  differ  only  in  the  numbers  of  their  sieves  and 
their  more  rapid  increase  at  the  end  of  the  break  process  for  break  semo- 
lina and  middlings. 

(5)  Diagrams  of  Sieves  for  Reduction. — As  in  the  preceding  cases  the 
diagrams   of  disposition   of  the   sieves  for  gifting   the   milled  product 
present  a  combination  of  throughs  and  overtails  differing  only  in  the 
numbers    of    their    sieves   and   the    number   of    "throughs    systems." 
This  diagram   of   sieves   should   be   employed  (a)  for  the  reduction  of 
middlings,  (6)  for  the  reduction  of  dunst  and  cleaning  the  offals,  (c)  for 
supplementary  machines. 

In  all  three  cases  the  chief  aim  of  the  reduction  is  to  obtain  flour. 
Therefore,  the  greater  number  of  sieves  in  this  diagram  should  be  set  for 
flour,  so  as  to  separate  the  large  product  more  accurately  during  the 
sifting  process. 

(a)  The  diagram  illustrated  by  Fig.  301  shows  the  position  of  the  sieves 
for  sifting  the  product  produced  by  the  reduction  of  middlings.  The 
highest  grades  of  flour  obtained  from  Russian  grinding  being  generally 
granular  (2  and  3  grades),  and  not  differing  in  size  from  middlings  No.  6 
and  dunst,  this  diagram  presents  two  varieties  of  sieves  :  the  first  flour 
numbers  yield  coarse  (granular)  flour,  the  second  soft  or  fine.  The 


Middlings 
Nos.  5-6. 


D 


CHAP,  v]  FLOUR   MILLING 

first  sieve  tails  over  the  required  product,  and  yields  semolina  Nos.  5  and 
6  ;  the  next  two  sieves  give  as  throughs  a  final  product  in  the  shape 
of  coarse  or  fine  flour,  as  required.  The  fourth  sieve  separates  semolina 
No.  6  from  the  dunst. 

We  must  note  the  fact  that  the  numbers  of  sieves  in  all  the  diagrams 
we  are  examining  depends  on  the  construction  of  the  sifting  machine  ;  it 
fluctuates  between  4  and  12.  If  the  number  of  sieves  is  higher,  more 
break,  middlings,  and  flour  sys- 
tems are  employed,  leaving  one 
dunst  sieve.  This  is  more  minutely 
described  in  the  milling  diagrams. 

(b)  The  diagram  of  sieves  for 
reduced   dunst   and   bran  differs 
from  the  preceding  in  that  the  last 
sieve  is  missing  and  the  numbers 
of  the  flour  sieves  are  higher  than 
usual  (from  Nos.  12  to  15),  for  the 
reduction  product,  if  the  pressure 
of  the  rolls  is  great,  gives  a  fine 
flour.     In  this  way  one    or  two 
sieves   yield   overtails,  separating 
the    dunst,    while    three   or   four 
give  flour  as   throughs,  the  last 
one  at  the  same  time  tailing  over 
the  finer  dunst. 

(c)  In  long   system   mills  the   flour   obtained  is  often  subjected  to 
control,  i.e.  the  middlings  (in  granular  grades)  or  dunst  (in  fine  flour)  are 
separated  away.     Then  the  diagram  resembling  the  one  on  Fig.  301, 
but  without  the  last  sieve,  with. a  less  number  of  sieves  (never  exceeding 
three)  must  be  used.     The   throughs   of  the  flour  sieves  give  the  final 
product,  while  the  tails  (middlings  or  dunst)  from  the  first  and  the  last 
sieves  are  returned  for  further  reduction. 


Middlings  „ 
No.  6     6 


<J              Nos. 

56-60 

<— 

t 

^~ 

«-      No.  5 

No.  11 

, 

I 

<- 

•«-     No.  5 

No.  13 

, 

<— 

<J                  No.  62 

* 

Dunst. 

FIG.  301. 


Ill 

THE  SIFTING  PROCESS 

Bolting  through  a  sieve  may  be  effected  only  if  the  product  on  its 
surface  moves  and  is  in  motion.  The  particles  of  product,  smaller  in  size 
than  thejneshes  of  the  sieve,  on  passing  through  the  mass  of  product  to 
the  bolting  surface,  will  fall  through  these  meshes. 


332  FLOUR   MILLING  [CHAP,  v 

An  inspection  of  the  reduced  product  shows  us  that  it  consists  of  par- 
ticles of  equal  specific  gravity,  but  different  in  size,  and  of  branny 
particles,  which  are  lighter.  For  this  reason  the  whole  of  the  product 
will  settle  on  the  sieve  in  layers,  according  to  specific  gravity.  The  top 
layer  will  consist  of  branny  particles  ;  the  layers  under  it,  equal  in  specific 
gravity,  will  find  their  depth  in  accordance  with  their  size,  the  smaller 
particles  lying  above  the  larger  ones.  Hence  it  is  clear  that  the  bolting 
system  requires  an  extremely  rigorous  stirring  of  the  product,  so  that 
the  small  particles  should  be  able  to  reach  the  bolting  surface  and  escape 
through  the  meshes.  By  shaking  the  sieve  in  this  manner  we  must 
break  up  the  natural  order  of  the  layers,  bringing  the  upper  layers  of 
small  particles  to  the  bottom,  and  the  large  to  the  top  for  tailing  over. 
That  is  why,  in  the  diagrams  we  have  reviewed,  the  number  of  flour  sieves 
which  yield  flour  as  throughs  is  larger  than  the  number  of  sieves  from 
which  overtails  are  derived. 

The  stirring  of  the  product  is  effected  either  as  in  reel-separators  of 
plain  action  (pp.  70,  71,  Figs.  58,  59,  60),  or  with  the  aid  of  beaters, 
which  catch  up  the  product  and  fling  it  upon  the  sieve,  or  again,  by  the 
influence  of  the  power  lying  in  the  plane  of  the  sieve  (p.  69,  Fig.  57). 
In  another  type  of  sifting  machines  the  power  acting  upon  the  product  is 
the  resultant  of  the  pressure  of  air,  perpendicular  to  the  direction  of 
motion,  and  a  power  parallel  to  that  motion.  In  these  machines  the  pro- 
duct is  divided  according  to  size  as  well  as  to  specific  gravity.  A  more 
rough  adaptation  of  this  method  of  stirring  the  product  we  saw  in  the 
grain -cleaning  machines  with  aspiration,  and  we  shall  see  it  applied  to 
the  reduction  product  in  purifiers  with  sieves. 

The  product  passes  through  the  sieve  influenced  by  its  proper  weight 
and  partly  by  the  pressure  of  the  layers  lying  above  the  particles  to  be 
sifted. 

Let  us  examine  the  favourable  conditions  necessary  to  allow  the 
particles  a  passage  through  the  sieve.  If  the  particle  a  (Fig.  302)  is  above 
the  sieve  AB  while  the  product  is  travelling  over  its  surface,  in  an  ordinary 
case  it  is  acted  upon  by  the  gravity  mg  (m  the  mass  of  the  particle,  and  g 
acceleration  of  the  gravity),  and  by  the  motive  power  T,  directed  upward 
at  an  angle  a  to  the  horizon.  This  direction  of  the  power  T  is  advantageous 
in  this  respect,  that  the  product  mixes  better,  the  larger  particles  at 
the  bottom  being  in  this  manner  brought  to  the  top.  But  the  incon- 
venience of  the  motive  power  directed  upwards  lies  in  the  fact  that  R, 
the  resultant  of  mg  and  T,  which  propels  the  particles  through  the  mesh 
of  the  sieve,  is  smaller  here  than  in  the  case  when  T  is  directed  down- 


CHAP.    V] 


FLOUR   MILLING 


333 


wards.  In  the  first  case  the  power  mg  is  diminished  by  Tlt  in  the  second 
it  would  have  increased  by  T ^  Besides  that,  in  the  second  case  the 
resultant  gm  and  T  form  a  wider  angle  with  the  plane  of  the  sieve  than 
in  the  first,  which  favours  to  a  greater  extent  the  passage  of  the  product 
through  the  sieve.  This  latter  circumstance  being  of  great  importance, 
we  shall  examine  it  more  minutely. 

Supposing  the  resultant  R  to  be  directed  to  the  surface  of  the  sieve 
at  a  right  angle  and  at  an  angle  ft  (Fig.  303).  If  the  direction  R  and  the 
surface  AB  of  the  sieve  form  a  right  angle,  then,  through  a  mesh  of  the 
c  size  the  particle  m  will  pass,  its  diameter  ab  being  almost  of  the  size  of  e. 
But  if  R  is  directed  at  the  angle  ft,  then  the  mesh  will  afford  passage  to 


'"1 


FIG.  302. 


FIG.  303. 


the  particle  m^  with  a  diameter  al  &1?  which  is  expressed  through  e  and 
the  thickness  h  of  the  sieve,  thus  : 


snce 


«!&!=«!/  sin  ft  =  (e—  h  Ctg  ft)  sinfi  =  e  sin(}—hGB, 
ajl=df=e  —  cd,  while  cd=h  Ctg  p. 

Hence  it  is  clear  that  the  diameter  of  the  particle  is  considerably 
smaller  than  the  side  of  the  mesh,  and  further  depends  on  the  thickness 
h  of  the  thread  too  ;  the  smaller  the  thickness  of  the  sieve,  the  larger 
the  particles  sifted  will  be,  and  vice  versa. 

If  we  take  a  middlings  sieve  No.  20,  which  has  e  =  l'l  mm.  (approxi- 
mately), and  h=Q-2  mm.,  then  the  direction  of  R  being  vertical,  the 
diameter  of  the  middlings  will  be  1  mm.,  and  h  here  has  no  influence  on 
the  size  of  the  middlings.  Let  us  suppose  now  that  R  lies  at  an  angle 
of  45°.  Then 


A/2 


mm. 


a161==csinj8— 
If  0=  30°,  then 

a161  =  l-lj—  0-2086=0-38  mm. 

In  other  terms,  in  the  first  case  (45°)  the  particle  which  can  pass 
through  the  mesh  is  almost  double  as  small  as  in  the  case  of  a  vertical  R. 


334  FLOUR    MILLING  [CHAP,  v 

When  R  lies  at  an  angle  of  30°,  a1b1=0'3S  mm.,  i.e.  almost  three  times 
as  small. 

From  the  above  we  may  conclude  that  the  more  favourable  condi- 
tions for  sifting  are  obtained,  when  R  is  perpendicular  to  the  surface  of 
the  sieve.  In  this  case  for  the  products  of  equal  size  the  number  of 
meshes  to  a  unit  of  the  bolting  surface  will  be  greater  than  when  R  is 
inclined.  The  number  N  of  threads  to  a  unit  of  length  will  be  : 


~h+e 

If  we  define  the  number  of  threads  to  1  cm.  for  the  three  quantities 
obtained  of  diapieters  of  the  particles,  we  come  to  the  following  : 

1Q  mm- 


N   _ 
1- 


0-2  mm.  +  ri  mm. 


10mm. 

2  0*2  mm.  +0'63  mm. 

10mm. 

3  0-2  mm.  +0-38  mm. 

This  answers  the  middlings  numeration,  Nl=2Q,  JV2^30,  and  JV,  =  38. 

Though  the  above  considerations  refer  to  one  particle  moving  over 
the  bolting  surface,  the  character  of  the  phenomenon  remains  the  same 
for  the  mass.  We  must  note,  however,  that  when  a  mass  of  product  is 
sifted,  there  is  no  such  sharp  difference  between  the  numbers  of  the 
sieves,  because  sifting  is  a  more  complex  process,  and  less  easily  analysed 
in  theory  than  we  have  outlined  it  in  respect  to  one  particle. 

Among  the  defects  of  an  horizontal  travel  of  the  product  we  must 
reckon  the  more  rapid  wear  of  the  sieves,  because  in  this  case  the  sharp 
edges  of  the  particles  of  product  act  as  incisors  upon  the  fibres  of  the 
sieves.  Thus  experience  mainly,  and  partly  the  elucidation  of  practical 
results  by  theory,  lead  us  to  the  following  conditions,  which  should  be  laid 
down  as  bases  for  us  to  build  our  estimate  of  the  working  surfaces  of 
the  sifting  machines  upon  : 

(1)  The  motion  of  the  product  to  be  sifted  over  the  bolting  surface 
should  be  such  as  to  keep  the  mass  of  product  continually  mixing. 

(2)  The  force  acting  upon  the  particles  should  act  in  a  direction  as 
near  as  possible  to  the  vertical. 

(3)  The  working  surface  of  the  sieve  must  be  fully  utilised  and  evenly 
loaded  with  product. 

If  the  construction  of  the  machine  answers  these  three  requirements, 
favourable  results  from  the  bolting  are  guaranteed, 


CHAP,  v]  FLOUR   MILLING  335 

IV 

CONSTRUCTION  OF  SIFTING  MACHINES 
1.  Reels  and  Centrifugals 

As  in  the  grain -sifting  machines,  the  machines  for  sifting 
the  products  of  milling  may  be  classified  in  two  groups  :  (1) 
machines  with  reciprocating  motion,  and  (2)  with  rotary  motion  of 
the  working  surfaces.  With  regard  to  the  outline  of  their  working 
surface  all  sifting  machines  are  likewise  divided  into  two  groups  : 
(1)  machines  with  flat  sieves,  and  (2)  machines  with  cylinder -shaped 
sieves. 

In  our  examination  of  the  bolting  machines  we  shall  commence  by 
turning  to  their  simplest  shapes,  i.e.  to  the  reel-separators. 

Polygonal  Reels. — The  constructions  of  polygonal  reel-separators 
for  grist  do  not  differ  materially  from  the  grain  reel-separators  de- 
scribed on  pp.  64  and  65.  In  large  mills  polygonal  reel-separators 
have  long  ago  been  displaced  in  the  milling  department  by  more  perfect 
machines.  But  since  it  is  cheap,  this  machine  is  often  set  up  in  small 
local  mills.  For  this  reason  we  give  the  data  of  capacity  of  the  poly- 
gonal reel-separators  (Table  XXXV,  p.  336). 

This  approximate  capacity  is  given  for  reel-separators  with  a  diameter 
of  700  to  850  mm.,  the  velocity  of  rotation  being  30  to  35  revolutions 
per  minute,  and  for  those  of  1000  mm.  in  diameter  and  running  at 
the  rate  of  28  to  30  revolutions,  their  incline  fluctuating  between 
5°  and  6°. 

Round  Reels.  —  Resting  upon  the  considerations  mentioned  on 
pp.  71  and  72,  we  regard  the  round  reel-separators  as  the  better 
type. 

The  incline  of  both  the  polygonal  and  the  round  reel-separators, 
owing  to  which  the  chain  wheels  and  belt-pulleys  have  to  be  set  on  the 
axes  in  an  inclined  plane,  must  be  reckoned  in  the  number  of  their  con- 
structive defects.  This  defect  is  evaded  in  the  new  constructions  by 
setting  screw  planks  in  the  prism  or  cylinder  of  the  reel-separator,  which 
propel  the  product  to  the  outlet  of  the  sieve  when  it  is  in  a  horizontal 
position. 

But  the  setting  of  these  planks  on  the  working  surface  of  the  reel- 
separator  is  inconvenient,  and  therefore  the  works  of  Thos.  Robinson 


336 


FLOUR   MILLING 


[CHAP,  v 


TABLE    XXXV 

CAPACITY  OF  PRISMATIC  REEL-SEPARATORS 


Dimensions  of  Prism  in  mm. 

Working 

Capacity  in  Ibs.  per  Hour. 

Power 

Area  in 

Consumption 

Diameter. 

Length. 

Square 
Metres. 

Break. 

Middlings. 

Flour. 

H.P 

1000 

1-75 

504 

180 

126 

0-10 

1250 

2-25 

648 

216 

162 

1 

1500 

2-70 

792 

288 

198T 

I     o-15 

1750 

2-30 

936 

324 

234 

r      \j  JL*J 

2000 

3-60 

1044 

360 

252 

1 

700 

2250 

4-08 

1188 

432 

288 

| 

2500 

4-56 

1332 

468 

324 

0-2 

2750 

5-00 

1512 

504 

360 

I 

3000 

5-50 

1620 

576 

396 

I     n-25 

3500 

6-46 

1872 

648 

468 

I        -  \J    —  *  ' 

4000 

7-40 

2160 

756 

540 

0-3 

1250 

2-78 

792 

288 

198 

} 

1500 

3-35 

972 

342 

234 

\    0-20 

1750 

3-95 

1152 

396 

288 

j 

850       - 

•  • 

•  • 

•  • 

•   • 

"   * 

:: 

4500 

10-34 

3024 

1044 

720 

0-5 

5000 

11-50 

3312 

1152 

1080 

0-6 

2000 
2500 

5-32 
6-72 

1548 
1944 

540 

684 

360 

468 

}     0-4 

1000 

•  • 

•  • 

•  • 

5500 

15-12 

4320 

1548 

1080 

0-8 

6000 

16-50 

4824 

1692 

1188 

0-9 

offer  the  construction  illustrated  on  Figs.  304  and  305.  On  the  shaft  of 
the  reel-separator  there  are  fixed  four  to  six  sprockets  or  more,  accord- 
ing to  the  length  of  the  reel-separator — to  which  there  are  lifters  bolted 
down  the  full  length  of  the  separator.  Into  these  lifters  there  are  freely 
set  the  tails  of  the  scrapers,  where  they  may  be  turned  by  means  of 
hand- wheels  with  common  rods.  At  one,  the  screw-threaded  end,  the 
rods  protrude  through  the  cross-heads  of  the  reel,  and  these  ends  are 
furnished  with  nuts  by  means  of  which  they  may  be  moved  backwards 
and  forwards,  thus  regulating  the  inclination  of  the  scrapers,  i.e.  increas- 
ing or  decreasing  the  thread  of  the  helical  surface  formed  by  the  scrapers. 


CHAP.    V] 


FLOUR    MILLING 


337 


During  the  rotary  motion  of  the  reel  together  with  the  beaters,  the 
product  falls  on  the  surface  of  the  beaters,  and  is  flung  back  upon  the 
cloth  cover  in  the  direction  of  the  outlet.  The  inclination  of  the  beaters 
determines  the  velocity  with  which  the  product  to  be  bolted  passes 


through  the  separator,  while  the  regulation  of  their  incline  imparts  a 
greater  or  a  smaller  velocity  to  the  motion  of  the  product.  We  have  met 
this  principle  already  in  Dobrovy  and  Nabholtz's  scouring  machine. 

Centrifugal  Dressing  Machines, — The  polygonal  and  the  round  reels 
of  the  ordinary  type  do  not  answer  the  second  and  third  conditions 

y 


338 


FLOUR    MILLING 


[CHAP,  v 


of  a  favourable  sifting  (p.  337).  In  fact,  the  force  imparting  motion  to 
the  product  is  the  component  force  of  gravity,  directed  parallel  to  the 
side  of  the  prismatic  reel  or  at  a  tangent  to  the  cylindric,  while  the  great- 
est sifting  area  is  one-third  of  the  whole  cover.  That  being  the  case, 
centrifugal  reel-separators  were  evolved,  the  purpose  of  which  is  to  compel 
the  product  to  move  at  a  more  or  less  wide  angle  to  the  bolting  surface, 
and  utilise,  if  possible,  the  whole  area  of  the  sieve.  To  attain  this  end, 
two  types  of  construction  of  the  centrifugal  are  made  :  one  of  them 
with  a  fixed  sieve-casing  containing  a  rotating  drum  with  helical 
beaters  which  catch  the  product  up  below  and  fling  it  upon  the  sieve  ; 

the  other  has  a  rotating  reel  and  in- 
clined beaters  rotating  within  it.  In  the 
first  construction  we  have  the  principle 
of  a  horizontal  scouring  machine,  in  the 
second,  that  of  a  bran -dusting  brush 
machine. 

The  adaptation  of  the  scouring  ma- 
chine principle,  however,  is  inexpedient 
here,  because  the  pressure  of  the  beaters 
through  the  product  upon  the  lower  part 
of  the  sieve  causes  the  bolting  cloth  to 
become  rapidly  worn  and  spoiled,  not  to 
speak  of  the  unnecessary  power  con- 
sumption. General  practice  has  rejected 
this  type  of  centrifugal,  and  we  shall 
therefore  pass  it  by. 

A    centrifugal   with    a   sieve   rotating 

in  the  same  direction  as  the  beaters  obviates  this  defect,  the 
beaters  being  set  at  such  a  distance  from  the  bolting  cloth  that 
they  cannot  scoop  the  product  up  from  below,  and  consequently  do 
not  tear  the  sieve.  The  operation  is  performed  in  such  a  manner 
that  the  rotating  sieve  lifts  the  product  and  drops  it  from  a  certain 
height  on  to  the  beaters,  which  throw  the  mass  to  be  bolted  to  the 
working  surface. 

Before  proceeding  to  describe  the  constructions  of  centrifugals 
of  the  second  type,  several  theoretical  considerations  must  be  adduced. 
The  first  and  the  third  conditions  necessary  for  the  sifting  to  be  satis- 
factory (the  mixing  of  the  product  and  utilisation  of  the  whole  working 
surface  of  the  sieve)  are,  evidently,  attained  in  the  centrifugal.  Now 
we  must  define  the  incline  of  the  working  surface  of  the  beater  to 


FIG.  305. 


CHAP,  v]  FLOUR    MILLING  339 

the   horizon,    when   the   product   rejected   will   fall   on    the  sieve  per- 
pendicularly to  the  element  of  the  cylindric  surface. 

The  particle  of  product  which  has  fallen  upon  the  beater  ab  (Fig/ 306) 
and  received  an  impact,  is  under  the  influence  of  the  gravity  mg  and  T  — 
mw,  where  w  is  the  acceleration  caused  by  the  impact  from  the  paddle. 
Examining  the  resultant  R  of  these  two  forces,  we  see  that  if  T  were 
directed  along  the  radius,  i.e.  normally  to  the  element  of  the  working 
surface,  the  force  mg  would  alter  this  direction.  Further,  the  force 
mg  will  likewise  alter  the  quantity  R  correspondingly  to  the  position  of 
the  beater  at  the  moment  it  strikes  the  particle.  Thus,  the  conditions  of 
sifting  on  the  whole  working  surface  of  the  reel  are  not  equal.  To  reduce 
the  action  of  the  force  mg  in  this  undesirable  direction  to  a  minimum, 
we  have  to  communicate  the  greatest  value  to  mw,  which  may  be  attained 


FIG.  306.  FIG.  307. 

by  the  beaters  running  at  high  speeds,  sometimes  6  to  10  metres  per 
second. 

Let  us  now  see  under  what  conditions  the  force  mw,  or  in  other  terms, 
the  velocity  of  the  impact  of  the  particle,  will  be  normal  to  the  working 
surface,  if  the  force  mg  is  ignored.  We  shall  suppose  first  that  the  cylinder 
and  the  paddles  are  rotating  in  one  and  the  same  direction,  and  prove 
that  only  in  this  case  will  mw  be  normal  to  the  surface  of  the  cylinder. 
If  R  is  the  radius  of  the  cylinder  (Fig.  307),  and  r  the  average  radius  of 
the  periphery  of  rotation  of  the  beaters,  the  circumferential  velocity  per 

second  of  the  cylinder  v^= — ^7:—,  where  m  is  the  number  of  revolutions 

bO 

per  minute,  and  the  average  circumferential  velocity  of  the  beaters 
v=  .  where  n  is  the  number  of  revolutions  of  the  beaters.  If  N  is 

O'  r 

the  resultant  velocity  with  which  the  product  strikes  the  sieve,  it  will 
then  be  normal  to  the  sieve,  when  the  velocity  Nlt  perpendicular  to  the 
paddle,  is  the  resultant  of  this  N  and  v0,  and  the  circumferential  velocity 


340  FLOUR    MILLING  [CHAP,  v 

of  the  paddles  V  ^=N  l  cos  a.     But  this  is  possible  only  when  the  beaters 
and  the  cylinder  revolve  in  the  same  direction. 

Marking  the  angle  between  F0  and  N  l  —  ft  we  find  that  K0=^i  cos  /?. 
But  according  to  the  condition  V  =N  ^  cos  a.  Therefore,  comparing  N1 
we  obtain  : 

v*  :  JL 

cos  ft      cos  a' 
or  substituting  the  values  of  I70  and  V  : 


60  .  COS  /?  ~  60  .  COS  a* 

After  reducing  : 

Em         rn 


COS  p       COS  a 

Since  L.EDF  =  9Q—P,   and    LOCD  =  $Q  +  a,  from  the  triangle 
we  obtain  : 


PC      r      sin90- 


_^ 
7?  ~~  sin  (90+  a)      cos  a 

Substituting  the  term  j-^=  |r  from  (2)  to  (x)>  we  find  : 


m      r 


This  correlation  shows  that  with  any  inclination  of  the  beaters  the 
direction  of  the  resultant  R  (Fig.  307)  may  be  made  normal  to  the  surface 
of  the  cylinder,  if  suitable  numbers  of  revolutions  and  radii  of  the 
reel  and  beaters  be  chosen.  In  inferring  this  correlativity  of  the  number 
of  revolutions  and  the  radii  the  gravity  of  the  product  was  not  taken 
into  consideration,  and  the  velocity  of  the  particle  was  supposed  to  be 
constant.  Practical  experience  corrects  this  formula  by  altering  the 
degree  of  ratio  of  the  radii  from  2£  to  3.  Finally,  therefore,  we  obtain  : 

m_  /  r\2J  —  3. 

»"VBy 

The  theoretical  considerations  of  Professor  Zworykin  given  here  find 
a  brilliant  corroboration  in  the  actual  construction  of  centrifugals,  the 
number  of  revolutions  and  the  diameters  of  which  we  proved  accord- 
ing to  his  formula,  having  obtained  a  great  accuracy  of  correlativity 
inferred.  In  this  way,  that  which  is  clear  from  simple  theoretic  infer- 
ences, practice  has  been  seeking  many  years,  until  it  reached  the  correct 
solution  of  the  question  after  groping  in  the  dark,  having  passed  a  lengthy 
number  of  rejected  unsuccessful  constructions  and  expended  much  money 
in  that  way, 


(3HAP.    V] 


FLOUR-  MILLING 


341 


Construction  of  Centrifugals. — Before  deciding  upon  the  modern 
type  of  a  reel,  the  works  offered  many  fairly  different  constructions 
of  these  machines.  We  shall  not  enumerate  these  types,  but  one 
of  them,  a  reel  from  the  works  of  Dost  in  Vienna,  which  at  a 
certain  period  was  very  popular,  demands  our  attention.  Fig.  308 
illustrates  a  cross  section  of  the  separator,  and  shows  its  reel  to  be 
of  a  star  section.  On  being  fed  into  the  reel  the  product  is  lifted 
on  the  platforms  6,  drops  from  a  certain  height,  and  is  caught  up  by 
the  beaters  c,  fixed  at  an  angle  to  the  generating  circle  with  two  or 
three  (according  to  the  length  of  the  reel)  sprockets  A.  The  incline  of 
the  bolting  side  a  is  so  chosen  as  to  have  the  product  rejected  by  a  blow 
from  the  paddles  fall  on  a  at  a  right 
angle.  The  sifted  product  is  conveyed 
by  a  worm  B  to  the  outside. 

We  have  already  seen  that  the  product 
can  fall  at  right  angles  on  the  sieves  in- 
dependently of  their  form.  If  this  sepa- 
rator did  work  satisfactorily,  evidently 
it  was  only  owing  to  the  happy  choice  of 
the  velocities  of  rotation  of  the  sieve  and 
the  beaters.  But,  speaking  generally, 
this  construction  is  less  successful  than 
that  of  the  ordinary  round  reels. 
In  the  first  place,  the  platforms  b  leave 
totally  unsifted  the  product  thrown  by 
the  beaters,  since  their  motion  is  parallel 
to  the  planes  of  these  platforms  lying  at  a  right  angle  to  a.  Further,  the 
construction  of  the  reel  is  rather  complex,  which  makes  clothing  it 
with  a  sieve  a  difficult  task.  Lastly,  the  wear  of  the  working  surface 
was  observed  to  be  uneven,  because  a  accepted  almost  the  whole  of 
the  work,  while  b  played  the  part  of  boxes  supplying  the  paddles  with 
product. 

Fig.  309  represents  the  modern  normal  type  of  a  centrifugal  dressing- 
machine  (Thos.  Robinson).  The  product  flows  to  the  feeder  A  and  is 
conveyed  by  the  worm  to  the  chamber  B  of  the  centrifugal.  The 
drum  C  containing  beaters  is  rotated  from  the  belt-pulley  1.  On  the 
shaft  of  this  drum,  at  the  opposite  end,  there  is  set  the  belt-pulley  2  from 
which  the  worm  D  is  brought  into  operation.  On  the  shaft  of  the  worm 
there  are  two  belt-pulleys,  4  and  6  ;  by  means  of  the  pulleys  4  and  5  the 
reel  is  rotated,  and  the  spiral  brush  E  for  cleaning  the  cloth  is  driven  by 


FIG.  308. 


342 


FLOUR   MILLING 


[CHAP,  v 


the  pulleys  6  and  7.  With  the  assistance  of  the  ribs  F  which  constitute 
the  frame  of  the  reel  the  product  is  lifted  to  a  certain  height,  and  then 
dropped  upon  the  beaters.  The  beaters  are  disposed  in  the  generating 
circle,  but  their  propellers  are  bent  to  a  helical  line,  as  shown  in  Fig.  310. 


FIG.  309. 


The  bearings  of  the  brushes  may  be  transposed,  so  that  the  brush  is 
approached  to  or  removed  from  the  sieve  according  to  its  wear  or  the 
necessity  of  a  more  rigorous  cleaning  of  the  bolting  cloth. 

Centrifugals  of  this  type  are  built  by  almost  all  European  works. 


10-tf 


FIG.  310. 

Very  rarely  the  beaters  bent  to  a  helical  line  are  discarded  and  solid 
beaters  arranged  at  an  angle  to  the  generating  circle  of  the  cylinder. 
Fig.  311  illustrates  a  perspective  view  of  Thos.  Robinson's  reel-separator 
furnished  with  such  beaters. 

Capacity  of  Centrifugals. —Since  almost   the  whole   of  the   working 


FLOUR    MILLING 


343 


CHAP.    Y] 

surface  in  the  centrifugals  is  utilised,  their  capacity  is  far  greater 
(nearly  fivefold)  than  that  of  the  ordinary  reels,  owing  to  which  they 
are  as  yet  not  everywhere  supplanted  by  plansifters  in  the  merchant 
mills.  They  are  generally  employed  for  sifting  the  products  of  the 


final  reduction,  i.e.  to  receive  them  from  the  smooth  rolls,  which  reduce 
the  middlings  and  dunst,  though  formerly  they  used  to  be  installed 
beginning  with  the  fourth  break.  Table  XXXVI  gives  us  the  capacity 
of  centrifugals  in  accordance  with  their  dimensions,  the  number 


344 


FLOUR   MILLING 


[CHAP,  v 


of    revolutions    of    the    cylinder,    and    of    the    drum    containing    the 
beaters. 

TABLE    XXXVI 
CAPACITY  OF  CENTRIFUGALS 


Dimensions  of  Cen- 
trifugal in  mm. 

Number  of  Revolu- 
tions per  Minute. 

Capacity  in  Ibs.  per  Hour. 

Horse- 
power 
Required. 

Diameter. 

Length. 

Cylinder. 

Beater 
Drum. 

Break. 

Rebreak. 

Middlings. 

Flour. 

610 
650 
700 
800 
900 
1000 

1500 
2000 
2500 
3000 
3500 
4000 

30 
30 
28 
26 
22 
20 

250 
250 
230 
200 
190 
180 

900-1080 
1260-1440 
1620-1800 
1980-2340 
2520-3060 
3240-3600 

828-900 
1152-1368 
1440-1620 
1800-1980 
2160-2520 
2880-3240 

540-720 
792-900 
972-1080 
1260-1440 
1620-1800 
1980-2160 

360-432 
540-612 
720-828 
900-1008 
1080-1260 
1332-1512 

1-0-0-4 
1-5-0-6 
1-8-0-8 
2-2-1-0 
2-8-1-2 
3-6-1-6 

As  concerns  the  power  consumption,  the  quantity  the  centrifugal 
separators  absorb  running  empty  amounts  to  80  per  cent.,  consequently 
their  useful  work  is  very  insignificant.  This  circumstance  is  the  cause 
of  their  losing  ground  to  more  economical  machines,  which  will  now 
occupy  our  attention. 

2.  Plansifters 

When  studying  the  reel-separators,  we  saw  that  this  type  of  sifting 
machine  does  not  allow  the  use  of  the  whole  working  surface  of  the 
sieves  (plain  reel-separators)  or  places  in  equal  conditions  of  work 
(centrifugals).  In  addition,  the  plain  as  well  as  the  centrifugal 
separators  consume  a  large  quantity  of  power.  These  defects 
induced  the  engineers  to  seek  a  more  perfect  type  of  machine,  which  was 
then  offered  by  the  Americans,  together  with  the  idea  of  an  automatic 
mill. 

Modem  technics  possess  two  types  of  plansifters,  differing  in  the 
character  of  motion  of  their  working  surfaces  : 

(1)  Machines  with  rectilinear  reciprocating  motion  of   the  working 

organs. 

(2)  Machines  with  gyrating  progressive  motion  of  the  sieves. 

(i.)  Machines  with  Reciprocating  Motion 

The  simplest  kind  of  such  a  machine  is  given  on  p.  31,  Fig.  28,  G. 
The  different  machines  of  the  "  Eclipse  "  (p.  64)  or  the  zigzag  separators 
are  more  perfect  types  of  it  And,  lastly,  Soder's  plansifters  may 


CHAP.    V] 


FLOUR   MILLING 


345 


be  pointed  out  as  one  of  the  best  modern  reciprocating  bolting 
machines  for  reduction  stock.  This  sifter  is  a  an  oblong  timber 
box  (Fig.  312)  supported  on  steel  spring  stands.  The  box  is  brought 
into  motion  by  an  eccentric  drive  with  a  counterweight  for  balancing 
the  inertia  of  the  mass.  Inside  the  box  (Fig.  313)  there  are  set  five 
bolting  frames. 

This  machine  can  very  successfully  do  the  work  of  a  reel  in  the 
small  farm  mills,  in  case  economy  of  space  is  a  great  consideration. 

Proceeding  now  to  give  an  estimate  of  the  reciprocating  machines,  we 
must  note  that  their  advantages  in  comparison  to  the  reel-separators 
consist  only  in  their  compactness.  On  the  other  hand,  they  have  material 


Ui 


1..      fc.        -«*(.*. 


FIG.  313. 


FIG.  312. 


Copper  cloth,  No.  26.    Silk  gauze,  Nos.  5  &  7. 
X  =  Inlet  of  stock. 


defects,  the  cause  of  which  lies  chiefly  in  the  character  of  motion  of  the 
machine.     These  defects  are  as  follows  : 

(1)  Necessity  of  considering  the  inertia  of  the  mass  of  the  machine. 

(2)  Variable  velocities  of  motion,   causing  an  unevenness  in  the 

bolting  of  the  product. 

Owing  to  these  defects,  the  application  of  reciprocating  machines  is 
very  limited.  It  is  only  their  comparative  cheapness  and  compactness 
which  makes  their  use  in  small  short  system  mills  possible. 


(ii.)  Machines  with  Gyratory  Progressive  Motion 

The  idea  of  the  constructive  principle  of  machines  of  that  type  is 
explained  to  us  by  G.  Luther's  grain-cleaning  machine  "Triumph," 
described  on  pp.  81,  82. 

The  main  parts  with  a  gyratory  progressive  motion  are  the  box, 
where  the  bolting  frames  are  arranged,  or  a  box  built  of  frames  joined  to 
each  other  and  covered  with  bolting  cloth  ;  then  drop -hanger  frames  or 
stands,  on  which  the  box  is  established,  and  a  shaft  with  an  eccentrically 
set  driving  finger.  The  diagram  of  that  sifter  is  given  on  p.  68,  Fig.  56. 


346  FLOUR   MILLING  [CHAP,  v 

When  the  shaft  A  is  in  rotation,  each  point  of  the  box  s  performs  a  gyra- 
tory progressive  motion. 

Before  passing  on  to  the  constructive  descriptions  of  machines  of  that 
kind,  we  must  decide  upon  the  fundamental  requirements  which  should 


JTIF 


3 


R 


FIG.  314. 


FIG.  315. 


be  answered  by  all  machines  of  the  type  in  hand,  and  prove  this  or  that 
construction  rational.     These  requirements  are  : 

(1)  Counterbalancing  the  centrifugal  force  ot  the  gyratory  motion 

of  the  working  organ,  the  details  of  the  transmission  of  motion 
being  of  the  least  possible  size. 

(2)  Utilisation  of  the  largest  area  of  the  bolting  surface. 

(3)  Simplicity  of  shape  and  setting  of  the  bolting  trays. 

(4)  Constant  cleaning  of  the  working  surfaces  to  avoid  blinding. 

To  be  able  to  make  our  estimate  of  the  sifters  from  the  point  of  view 
of  the  above  requirements,  it  is  necessary  to  become  acquainted  with  the 
main  types  of  construction. 

K.  Haggenmacher's  Sifter. — The  plansifter  which  brought  about  a  re- 
volution in  bolting  methods  was  invented  by  a  citizen  of  Switzerland, 


FIG.  316. 

K.  Haggenmacher,  at  the  end  of  the  eighties  of  the  last  century.  The 
original  construction  of  this  sifter  is  shown  in  Fig.  314.  The  box  R, 
containing  the  bolting  trays,  is  suspended  on  four  rods  g,  and  is  brought 
into  motion  from  the  driving  pulley  d  by  a  quarter-twist  belt  drive  to  the 
receiving  pulley  d.  This  pulley  and  the  fly-wheel  L,  with  a  counterweight 
at  K,  have  a  common  shaft,  furnished  with  a  collar  a,  with  which 
it  rests  on  the  bearing  in  the  cross-head  T.  The  hub  of  the  fly-wheel 


CHAP.    V 


FLOUR   MILLING 


347 


FIG.  317. 


t) 


L  has  an  eccentrically  set  journal,  cast  in  one  piece  with  the  hub  ;   this 

journal  enters  into  the  bearing  of  the  cross-head  S,  coupled  with  the  frame 

N,  on  which  the  box  R  with  the  sieves  is  set.     The  rods  g  are  set  (Fig.  315) 

in  ball-bearings  n.       The  product  flows   in 

down  the  spout  E  through  a  linen  sleeve  Gl 

and  is  delivered  after   the   sifting  through 

similar  sleeves  G2.  whence  it  is  directed  for 

further  treatment,  or  into  bins,  if  it  is  flour. 

For  setting  the  sifting  box  in  a   horizontal 

position,   the    rods    g,    consisting    of    two 

pieces,   have  nuts    t,    by  means    of    which 

the  lower  piece  of  the  rod  may  be  screwed 

into  the  hub  r,  provided  with  a  screw  thread,  thus  making   the  rods 

shorter  or  longer.     A  longitudinal  section  of  a  box  with  five    trays  is 

shown  on  Fig.  316,  their  fixing  on  Fig,  317. 

*  The   sieves    of    that    sifter 

lying  in  a  horizontal  plane,  the 
product  travels  with  the  aid 
of  slats,  which  operate  in  the 
manner  described  on  p.  69, 
Fig.  57.  This  diagram  shows 
us  that  the  direction  of  the 
progressive  motion  of  the  pro- 
duct coincides  with  that  part 
of  its  gyrating  motion  which 
is  in  opposition  with  the  arrow 
of  the  setting  of  the  slats. 
The  different  shapes  of  the 
slats  (of  zinc  sheet  iron)  sug- 
gested by  Haggenmacher  are 
given  on  Fig.  318,  but  the 
straight  slats  set  at  right 
angles  to  the  direction  of  the 
motion  (part  y)  proved  to  be 
the  most  practical.  If  the 

slats  are   arranged  as   shown   on   Fig.   318,   then   the   product   fed   in 

through  A  at  the  top  will  move  along  the  arrows  s.     The  frame  here  is 

divided  by  a  partition,  and  its  right  and  left  part  work  independently, 

directing  the  overtails  to  the  outlet  B. 

To    get   a    clear   notion    of    the  sifting  operation,  we  shall  review 


W^M^ 
f*          k _.._.•*  * 

>  ,1.  s         ,1  ^ 


lit*  I::J 


IliJ 


FIG.  318. 


348  FLOUR   MILLING  [CHAP.  V 

the  diagrams  of  the  disposition  of  trays  for  break  and  reduction 
stocks. 

The  break  product  runs  to  the  first  and  to  the  second  sieves  (Figs.  319 
and  320)  simultaneously  and  travels  to  the  right,  giving  break  semolina 
as  overtails,  and  the  remaining  product  as  throughs.  The  product  of  re- 
breaks  may  be  directed  to  the  second  sieve,  if  it  is  calculated  for  rebreak 
semolina.  If  the  break  product  go  only  to  the  first  frame,  it  will  tail  over 
the  break  semolina  of  the  next  order  discharged  through  6,  and  bolt  the 
rebreak  semolina  and  the  rest  of  the  products.  On  the  second  sieve  the 
products  travel  in  the  same  direction,  and  therefore  yield  rebreak  semo- 
lina as  tails  delivered  out  of  the  sifter  through  c,  while  the  remaining 
middlings  and  flcur  pass  through.  The  next  sieve,  No.  3,  is  designed 
to  overtail  the  coarse  middlings,  beginning  with  No.  1,  the  throughs 
at  the  same  time  passing  to  the  fourth  linen  (or  sheet-iron) 

tray,  where  the  slats  are  so 
disposed  as  to  propel  the  product 
in  the  opposite  direction.  On 
reaching  the  openings  e  the  pro- 
duct falls  from  the  sheet -iron  tray 
on  to  the  fifth  sieve,  which 
FIG.  3l9.-Diagram  of  Longitudinal  Section  through  the  openings  e,  gives  the 

of  Sieves. 

fine  middlings  and  dunst  as  tails 

to  the  seventh  sieve,  and  throws  the  flour  upon  the  cloth  of  the  sixth 
tray  as  throughs,  which  is  delivered  through  /.  The  bolting  tray  7  is 
divided  into  three  sections  with  different  cloths,  which  yield  dunst  and 
fine  middlings  as  throughs,  and  tail  over  fine  middlings  which  are  larger 
than  those  of  the  throughs. 

In  this  way  the  three  first  sieves  operate  by  the  "  overtails  system  " 
and  the  two  last  ones  by  the  "  system  of  throughs."  The  throughs  from 
the  bolting  frame  7  fall  on  the  bottom  8  in  which  there  are  holes  h,  hl  and  h2 
for  letting  the  dunst  and  the  fine  middlings  out.  The  frames  1,  2,  3,  5, 
and  7  are  called  the  working  trays,  while  those  of  linen  or  sheet  iron,  4,  6 
and  8  are  called  collecting  trays.  This  diagram  contains  only  one  flour 
tray,  5,  but  to  have  the  flour  more  accurately  sifted  there  are  two  or  even 
three  flour  trays  set  in  case  a  large  quantity  of  break  flour  is  yielded. 
The  blinding  of  the  sieves  3,  5  and  7  is  overcome  with  the  aid  of  shakers, 
which  will  be  spoken  of  later. 

The  diagram  of  the  trays  for  the  stock  reduced  on  smooth  rolls  is  shown 
on  Figs.  321  and  322.  Since  those  products  present  a  mixture  of  fine 
middlings  and  dunst  with  a  considerably  preponderating  quantity  of 


CHAP.    Vj 


FLOUR    MILLING 


349 


flour,  the  sifting  away  of  the  latter  offers  greater  difficulties  than  in  the 
first  case.  For  this  reason  each  working  tray  is  succeeded  by  a  collecting 
one,  and  the  process  of  sifting  is  done  on  the  following  lines.  The 
bolting  working  frame  1  with  cloth  No.  60  xx  receives  the  reduced 


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FIG.  320. — Plans  of  Sieves  and  Linen  Frames 


stock  and  yields  fine  middlings  as  tails,  which  is  ejected  from  the  sifter  at  c 
through  all  the  trays.  The  dunst  and  flour  go  to  the  cloth  of  the  collect- 
ing tray  2,  down  which  they  travel  in  the  opposite  direction  and  are 
passed  to  the  working  tray  3  with  a  dunst  sieve  No.  5  xx,  tailing  over  the 


350 


FLOUR    MILLING 


[CHAP,  v 


coarser  dunst,  which  is  directed  to  its  exit  through  d.  The  throughs 
from  the  third  tray  travel  over  the  fourth  cloth  through  the  openings 
dt  to  the  working  tray  5  clothed  with  sieve  No.  12,  which  yields  finished 


c-Sieve 
n — Linen 
d— Bottom 
p— Grate 
e— Sheet  Iron 


FIG.  321. Diagram  of  Longitudinal  Section  of  Sieves. 

flour  as  throughs,  to  be  delivered  through  the  outlet  e.  The  tails  from 
the  fifth  tray  go  to  the  last  working  surface  7,  furnished  with  flour 
sieves  of  different  numbers  (Nos.  12  and  13),  which  sift  flour  through  on 
to  the  collecting  bottom,  and  tail  over  the  finest  dunst.  Consequently, 


— ,    -73 


Uf <%* 


H- 


o 


r   ^ 


O 


'^ 


5-Shakers. 


D—  Bottom. 


FIG.  322. 

i,  3,  5,  &  7  are  sieves. 


2,  4  &  6  are  cloths. 


the  first  two  sieves  here,  1  and  3,  are  operating  on  the  ''overtails 
system,"  separating  away  the  fine  middlings  and  dunst  or  dunst  only  (this 
depends  on  what  the  product  ground  on  the  smooth  rolls  is,  whether  it 


CHAP,  v]  FLOUR    MILLING  351 

is  coarse  or  fine  middlings),  and  the  sieves  5  and  7  on  the  '  throughs 
system,"  yielding  ready  stock. 

In  the  first  diagram  there  are  marked  three  sifting  trays  with  shakers, 
in  the  second  four.  It  has  already  been  mentioned  that  the  shaking  of  the 
sieves  is  necessary  to  clean  the  meshes  blinded  with  product.  The  trays 
1  and  2  of  the  first  diagram  need  no  shaking,  the  sieves  being  fairly  open 
(Nos.  20  and  28,  wire),  besides  which  the  product  is  sufficiently  coarse  to 
clear  the  meshes  by  the  pressure  of  its  mass.  For  the  silk  sieves, particularly 
those  for  dunst  and  for  flour,  which  dress  through,  a  tapping  action  to 
keep  them  clean  is  indispensable,  and  is  performed  generally  by  means  of 
large  wheat  grain,  gutta-percha  balls,  or  the  grains  of  leguminous  plants. 

Let  us  watch  the  travel  of  the  tapping  grains  in  the  second  diagram. 
Down  the  same  spout  with  the  product,  or  along  a  separate  one,  the  grains 


Section  throuyh  A  B. 


Section  through  C  D. 


A-\ 


FIG.  323. 


FIG.  324. 


FIG.  325. 


of  wheat  or  pease  are  conveyed  to  the  first  tray  and  run  over  the  sieve, 
shaking  it,  being  bodies  of  greater  weight.  On  reaching  the  slat  PQ, 
and  falling  upon  an  open  wire  cloth,  the  product  passes  through  it,  while 
the  tappers  travel  over  it  and  turn  in  the  direction  indicated  by  the 
arrow  to  the  openings  6,  through  which  they  pass  on  to  the  cloth  of  tray  2 
and  proceed,  together  with  the  product,  to  the  left.  Once  arrived  at  the 
opening  cl  the  product  and  tappers  pass  on  to  the  sieve  3,  and  again  in 
the  same  manner  go  to  the  cloth  4.  Then  through  openings  d±  and  d2 
they  fall  successively  upon  the  sieves  5  and  7.  From  the  tray  7,  passing 
the  open  wire  cloth  by,  the  tappers  fall  out  at  the  outlet  bl  to  the  ele- 
vating mechanism,  which  carries  them  again  to  frame  1.  The  elevating 
mechanism  is  a  vertical  worm  with  a  small  thread,  stationed  on  the  outside 
or  inside  the  section. 

Figs.  323,  324  and  325  show  the  elevation  of  the  tappers  disposed  inside 
the  box.     Here  inclined  planes  are  used  in  the  place  of  a  worm.     From 


352 


FLOUR    MILLING 


[CHAP,  v 


the  last  sieve  (Fig.  323),  having  run  over  the  open  wire  cloth,  through 
which  the  product  passes  to  the  outlet  spout,  the  tappers  reach  the  first 
inclined  plane,  along  which  they  ascend  to  the  first  horizontal  plane,  in- 
fluenced by  shocks,  effected  by  the  rotation  of  the  sieve.  From  the  first 
landing  they  ascend  to  the  second  over  an  inclined  plane  having  a  retro- 
grade motion,  then  to  the  third,  and  so  on  to  the  first  bolting  tray.  During 
all  the  time  of  the  work  each  sifting  tray  should  be  covered  with  tappers 
which  form  an  uninterrupted  chain  covering  the  sieves  and  stretching 
through  the  elevator.  Generally  the  tappers  from  the  last  sieve  are 
carried  to  the  first.  But  sometimes  in  the  vertical  canal  there  are  made 


FIG.  326. 

openings  E  to  the  nearest  trays,  owing  to  which  part  of  the  tappers  fall 
on  the  trays  with  the  openings  E,  and  part  ascend  to  the  first  tray. 

Fig.  324  illustrates  the  plan,  and  Fig.  325,  a  section  through  CD, 
which  make  the  construction  clear.  On  Fig.  326  may  be  seen  the 
general  disposition  of  such  a  cleaning  device. 

The  defects  of  cleaning  the  sieves  by  means  of  tappers  consist  in  the 
fact  that  the  sieves  have  to  be  overloaded  with  superfluous  weight,  which 
are  a  cause  of  their  rapid  wear.  The  other  shakers,  such  as  spiral  springs, 
chains,  &c.,  have  the  same  defects. 

To  obviate  these  defects  the  shakers  are  sometimes  displaced  by 
brush  cleaners,  which  are  diagrammatically  shown  on  the  same  Fig.  326 
(cleaning  of  the  second  sieve).  The  wooden  rod  A  has  soft  hair  brushes 


CHAP.    V] 


FLOUR    MILLING 


353 


at  the  top  and  the  bottom,  and  the  working  upper  part  of  the  brush  touches 

the  lower  surface  of  the  sieve,  while  the  other  end  rests  on  a  sheet-iron 

tray.     At  the  end  of  the  rod,  free  of  the  brushes,   there  is  a  timber 

finger  a,  which  enters  into  the  guiding  canal  BC  and  prevents  it  from 

moving  to  the  right  or  to  the  left.     When  the  sieve  is  in  motion  the  brush 

travels  along  one  side  of  the  channels,  turns  back  on  reaching  their 

corners,  and  runs  along  the  other  side. 

The  brushes  clean  the  sieves  better,  if  the  hair  is  sufficiently  soft, 

influence  their  wear  very  little,  and  therefore  brush  cleaning  has  been 

adopted    by   almost    all   makers.       This 

cleaning,  however,    has   its   own,  though 

insignificant,  defects.      In  the  first  place, 

the    guiding    channel    annuls    a    certain 

part     of    the    working    surface    of     the 

sieve,  and  secondly  the  corners   of    the 

bolting     trays     remain     untouched     by 

the    brush     and    are    consequently    not 

cleaned. 

The  product  travels  in  the  channels 
of  the  trays  of  the  sifters  with  the 
aid  of  slats,  as  we  have  seen ;  the 
speed  of  motion  depends  on  the  number 
of  revolutions  and  the  degree  of  eccen- 
tricity defining  the  radius  of  rota- 
tion of  each  point  in  the  sifter.  The 
degree  of  eccentricity  defines  the 
width  of  the  main  channels  on  the  trays. 
For  an  explanation  of  this  pheno- 
menon we  shall  turn  to  Fig.  327.  The  radius  of  rotation  of  each  particle 
of  product  on  the  sieve  is  equal  to  the  degree  of  eccentricity.  The  larger 
this  radius,  the  greater  is  the  wave  of  the  curve  AB,  of  the  resultant 
motion  of  the  product  under  the  influence  of  centrifugal  force,  of  the 
impact  from  the  slat,  and  of  gravity.  If  the  channel  taken  is  too 
broad,  we  shall  have  immobile  dead  masses  Q.  To  move  these  masses 
also,  the  slats  could  be  made  longer ;  but  then  we  should  obtain 
dead  masses  Qi  between  the  slats.  The  question  concerning  the 
normal  width  of  the  channels  and  the  length  of  the  slats  is  solved  by 
general  practice,  since  it  cannot  be  solved  theoretically,  the  quantity 
of  the  force  of  friction  being  indefinite.  General  practice  gives,  for 

instance,    the    following    correlation    of    the     number    of   revolutions, 

z 


FIG.  327. 


354 


FLOUR   MILLING  [CHAP,  v 

the  width  of  the  channel,  and  the  radius  of  rotation  (Table  XXXVII, 
European  works) : 

TABLE    XXXVII 


Number  of  Revolu- 
tions per  Minute. 

Radius  of  Rotation 
in  mm. 

Width  of  Channel 
in  mm. 

190 

90 

220 

200 

85 

170-200 

210 

80 

170 

220 
220 

75 
70 

160 

• 

140 

240 

65 

140 

We  must  say,  however,  that  these  average  values  of  the  elements  of 
the  sifter  and  its  motion  do  not  give  uniform  work  as  regards  quantity 
as  well  as  quality  for  each  bolting  tray.  Since  each  tray  operates  with 
products  of  various  sizes,  the  coefficients  of  friction  of  the  product  against 
the  sieve  for  each  tray  are  likewise  different. 

In  practice  the  values  given  in  the  table  are  generally  decided  upon 
in  accordance  with  results  of  the  work  of  the  dunst  and  the  flour  sieves, 
where  a  small  number  of  revolutions  causes  a  choking  up  of  the  sifter,  i.e. 
the  channels  become  blocked  with  product,  which  does  not  move  forward 
and  so  chokes  the  machine.     A  high  speed  is  also  injurious  to  the  work, 
because  the  overtails  will  contain  a  large  amount  of  floury  particles  if  the 
product  travels  rapidly.      However,  a  normal  speed  of  motion  of  the  fine 
and  mealy  product  corresponds  to  too  great  a  velocity  for  the  mixture  of 
coarse  (break,  rebreak,  middlings  Nos.  1  to  3),  and  fine  products  previous  to 
their  separation,  owing  to  which  the  overtails  will  consist  of  fine  middlings, 
dunst,  and  flour.     That  being  the  case,  Professor  Zworykin  very  justly 
considers  that  the  sieves  grading  fine  middlings,  dunst,  and  flour  should 
be  inclined  upwards  in  the  direction  this  product  travels,  to  reduce  the 
velocity  of  its  motion.     Then  it  would  be  possible  to  choose  a  number  of 
revolutions  for  the  sifter  favourable  to  an  efficient  sifting  both  for  coarse 
and  fine  products.     It  is  to  be  regretted  that  this  simple  idea  has  not 
been  utilised  by  any  of  the  works,  although  its  realisation  would  have 
imported  practically  no  constructive  complications  into  the  sifter. 

Bunge's  Round  Bolter. — Haggenmacher's  sifter  was  succeeded  by  a 


CHAP.    V] 


FLOUR    MILLING 


355 


round  bolter  designed  by  Bunge  ;  the  scheme  of  its  construction  is  as 
follows  (Fig.  328)  :  A  cylindrical  box  consists  of  separate  rings  b  coupled 
together  by  bolts  c  symmetrically  at  four  points  and  suspended  on  three 
or  four  reed  or  steel  rods  I1.  The  box  is  brought  into  a  gyratory  pro- 
gressive motion  by  means  of  a  finger  i  set  eccentrically  to  the  shaft  hlt 
In  the  box  there  are  fixed  round  bolting  trays  a  and  trays  «3  with  conic 
discs  e,  having  the  same  function  as  the  cloth  in  Haggenmacher's 
sifter.  The  product  flows  down  the  spout  d  along  the  axis  of  the  sifter 
and  falls  upon  the  sheet-iron  cone  D,  whence  it  evenly  descends  to  the 
sheet-iron  cone  e5  with  a  slighter  incline.  Over  the  cone  e5  the  product 
runs  to  the  ring  &,  where  it  falls  on  an  open  sieve  A,  which  yields  the  large 


FIG.  328. 

product  as  tails  and  the  rest  as  throughs.  The  tails,  having  passed  down 
the  axis  spout  /,  drop  on  the  conic  bottom  (7,  and  is  directed  to  the  out- 
let spout  /j.  The  throughs  pass  to  the  sheet-iron  cone  e  and  fall  on  the 
sieve  B.  The  further  motion  of  the  product  is  clearly  seen  in  the  drawing. 
The  sieves  B  and  C  give  flour  as  throughs,  which  is  discharged  through 
spout  e2,  and  tail  over  middlings  delivered  by  the  spout  /2.  Under  the 
sieves  there  are  arranged  the  brushes  KL  fixed  to  angle-iron  rings  k, 
which  are  freely  set  on  timber  rings  »3,  and  rest  on  flat  rings  o.  The 
brushes  are  brought  into  rotary  movement  by  the  motion  of  the  sifter, 
and  remove  any  stock  blocking  up  the  meshes  of  the  sieves. 

An  end  elevation  of  Bunge 's  bolter  is  given  in  Fig.  329. 

Instead  of  the  conic  sheet-iron  discs,  in  the  models  of  a  later  date 
horizontal  flat  discs  were  recommended,  with  slats  on  the  outer  and 


356 


FLOUR   MILLING 


[CHAP,  v 


inner  rings,  while  American  engineers  offered  spirally  disposed  combs, 
as  shown  in  Fig.  330.  Here  we  have  a  working  tray  over  which  the  pro- 
duct travels  from  the  axis  to  the  periphery  by  a  spiral  route. 

Before  proceeding  to  give  a  comparative  estimate  of  the  merits  and 
demerits  of  the  square  and  round  bolters,  we  must  become  acquainted 
with  yet  another  type  of  sifters. 

Konegen's  Sifter. — The  two-box  sifter,  built  by  the  Amme-Giesecke 
and  Konegen  works,  is  a  modified  construction  of  the  two-box  sifter 
first  invente^  by  Engineer  Konegen,  who  set  himself  the  problem  of  giving 


FIG.  329. 


FIG.  330. 


a  balanced  motion  to  the  machine.  The  circumstances  favourable  in 
dynamical  respect  to  the  work  of  two-box  sifters  will  be  examined 
below ;  at  the  present  moment  we  shall  turn  to  the  modern  construction 
of  Konegen's  sifters. 

According  to  the  way  in  which  the  boxes  or  blocks  of  the  sifters  are 
erected,  two  types  are  distinguished  :  one  suspended  by  means  of  four 
cane  rods  (Fig.  331),  and  one  in  which  the  boxes  are  supported  on  four 
stands  (Fig.  332).  The  manner  in  which  the  boxes  are  hung  is  their 
sole  difference. 

The  sifter  boxes  are  built  of  separate  trays.     The  bottom  or  collecting 
tray  of  the  first  sifter  is  screwed  on  to  two  rods  fixed  to  the  main  frame 
and  the  other  trays,  numbered  in  corresponding  order,  are  laid  upon  it' 


FLOUR   MILLING 


357 


CHAP.    V] 

When  the  trays  of  each  box  are  fitted  up,  they  are  coupled  together  by 
four  bolts  fixed  on  joints  to  brackets  bolted  to  the  main  frame,  which 


FIG.  331. 


consists  of  two  parallel  H-iron  beams  •/,  joined  by  a  third  cross-beam, 
The  suspended  types  have  riveting  sets  for  cane  rods  on  their  longi- 

v 


L 


FIG.  333. 


tudinal  beams,  while  those  supported  have  brackets  fixed  for  the  stands. 
The  stands  have  the  following  arrangement  (Fig.  333)  :  The  foundation 
is  a  cast-iron  box  containing  a  plate  of  the  same  metal  with  a  leather 


358 


FLOUR   MILLING 


(CHAP.  V 


lining  soaked  in  oil.  A  cast-iron  shoe  for  the  steel  stand  is  set  in  the 
plate.  The  shoe  and  the  plate  are  covered  with  a  casing.  Into  the 
stand  there  is  screwed  a  bearing  i  for  the  ball  vertical  journal  Z,  which  is 
screwed  into  the  bracket  b,  attached  to  the  longitudinal  H-iron  beam.  A 
lubricator  K  is  screwed  on  the  bearing  i,  and  a  cap  M  on  the  vertical 
journal  Z  to  give  the  stand  a  more  elegant  appearance. 

The  footstep  S  for  the  shaft  transmitting  the  motion  is  set  in  a  drop- 
hanger  frame,  and  its  bearing  in  the  frame  alf  The  shaft  W  is  joined  to 
the  fly-wheel,  which  has  a  counterbalance,  by  means  of  the  hub  h  of  the 
fly-wheel,  screwed  on  the  threaded  part  of  the  shaft.  For  lubrication  there 
is  the  cup  o,  out  of  which  the  oil  runs  into  the  bearing  (Fig.  334).  The 
cup  o  is  supplied  with  oil  from  the  outside. 

On  Fig.  335  is  shown  the  balance-wheel  from  the  top.     Between  the 


FIG.  334. 


FIG.  335. 


adjustable  weights  w,  serving  for  additional  regulation,  there  is  a  box 
filled  with  lead.  The  finger  k  of  the  balance-wheel  enters  into  the 
adjustable  bearing  enclosed  in  the  cast-iron  frame,  which  is  fixed  between 
longitudinal  H-iron  beams.  With  the  aid  of  bolts  b  the  hub  of  the 
bearing  may  be  adjusted  to  set  it  correctly  when  erecting  to  alter  the 
degree  of  eccentricity.  A  perspective  view  of  the  Konegen  sifter  is 
shown  in  Fig.  336. 

A  Two-box  Sifter  by  "  Seek  Bros."  Works.— The  plansifter  shown 
in  Figs.  337  and  338  is  a  model  of  a  two-box  balanced  sifter  of  the 
newest  type.  The  left-  and  right-hand  side  boxes  are  joined  by  a 
timber  frame  of  joists  in  a  square  section.  The  frame  coupled  together 
between  the  boxes  by  two-angle  channel  irons  forms  the  base  of  the 
sifter.  On  the  one  side  of  this  frame  on  the  stands  e  and  supports,  rest 
both  the  boxes  of  the  sifter,  which  are  a  series  of  sieve  trays  arranged  in 
stories,  and  coupled  together  by  rods  h,  fastened  with  one  end  to  the 


FLOUR   MILLING 


359 


CHAP.    V] 

frame  ;   on  the  other  side  the  frame  couples  in  with  the  fly-wheel  e  and 
the  shaft  6,  which  impart  a  gyratory  motion  to  the  sifter. 

We  shall  first  direct  our  attention  to  the  dismantling  of  the  boxes 
and  the  erection  of  the  sifter.  The  rods  h  are  fastened  by  joints  to  the 
frame.  The  top  ends  of  the  rods  entering  into  the  slots  of  the  cast-iron 


FIG.  336. 

cross-bars  over  the  boxes  have  a  screw  thread,  and  with  the  aid  of  nuts 
allow  the  frame  of  the  sifter  to  be  tightened.  When  the  sifter  is  to  be 
taken  apart  the  nuts  are  loosened,  the  rods  turned  down,  and  the  cross- 
bars removed,  then  the  bolting  trays  are  taken  off  one  after  the  other. 
The  bolting  trays  from  the  lower  part  of  the  box  are  removed  downwards 
after  the  rods  have  been  loosened. 


360 


FLOUR   MILLING 


[CHAP,  v 


As  mentioned  above,   the   whole  mass   of  'the   sifter   is   supported 
on  four  stands.     The  stand  is  an  iron  rod  e  (Fig.  338),  which  carries  a 


ball  bearing  at  its  upper  end,  and  a  buffer  vertical  journal  g  resting  on  a 
flat  bearing  gl  at  the  other  end.     Between  the  buffer  and  the  bearing  a 


FLOUR   MILLING 


361 


CHAP,  v] 

piece  of  leather  is  placed  to  lessen  shock.  The  ball  vertical  journals 
fixed  to  the  frame  of  the  sifter  rest  on  the  footsteps  /,  and  in  this  manner 
the  sifter  is  supported  on  rods  e.  The  rods  e  being  always  set  aslant 
in  respect  to  the  vertical  axis  of  the  sifter,  it  is  evident  that  the  horizontal 
component  of  the  weight  of  the  sifter  is  communicated  by  pressure  on 
the  shaft  b.  . 

Since  the  rods  constitute  one  of  the  most  essential  details  of  a'sifter, 


Fia.  339. 


FIG.  340. 


two  other  types  of  rods  evolved  by  Seek  should  be  described,  and  more 
minutely. 

Fig.  339  illustrates  a  rod  built  of  two  parts  connected  by  a  two- 
twist  nut  which  affords  the  possibility  of  adjusting  the  length  of  the 
rod. 

The  stem  a  is  connected  by  joints  "6  and  bl  with  boxes  c  and  c1, 
which  roll  over  the  bearing  surfaces  d  and  d1.  One  of  the  surfaces  (the 
top  one)  is  fixed  to  the  frame  of  the  bolting  machine,  the  other  lies  on 
the  ground.  In  the  drawing  we  may  see  that  the  journals  of  the  joints 
are  turned  at  an  angle  of  90°  in  respect  to  each  other. 


362 


FLOUR   MILLING 


[CHAt>.    V 


Each  one  of  the  boxes  on  the  side  next  to  the  support  is  cylindrical  in 
shape,  and  the  axis  coincides,  or  nearly  coincides,  with  the  axis  of  the 
journal  of  the  joint  lying  opposite.  The  box  freely  swings  to  either  side 
as  far  as  is  necessary  for  the  circular  motion  of  the  sieve. 

To  prevent  the  sieve  when  operating  from  running  out  of  the  limits  of 


FIG.  341. 

the  motion  required,  the  bearing  surfaces  of  the  boxes  towards  their 
rims  are  bound  by  planes  tangent  to  the  cylindric  surfaces  of  the  boxes. 

Fig.  340  illustrates  the  second  type  of  support,  Here,  different  from 
the  preceding  case,  the  boxes  with  the  mutually  perpendicular  planes  of 
swinging  are  transferred  to  one  end  of  the  prop  in  such  a  way  that  the 
top  one  swings  over  the  back  of  the  one  below.  Thus,  both  the  boxes 


CHAP.    V] 


FLOUR   MILLING 


363 


form  the  bottom  joint,  which  at  the  same  time  keeps  the  swinging  rod 
from  turning  over. 

The  top  end  of  the  rod  is  connected  with  the  box  of  the   bolting 
machine  by  means  of   an    or- 
dinary     universal      (Hooke's) 
joint. 

The  upper  box  c  rests 
on  the  flat  back  of  the  box 
c1,  which  has  its  plane  of 
swinging  turned  at  an  angle  of 
90°.  The  lower  box  lies  loose 
in  the  box  d,  and  on  its  back 
has  flanges  c2,  serving  to  direct  FlG  342 

the  box  c. 

The  sifter  is  brought  into  motion  in  the  following  manner  :  the 
shaft  b  with  a  driving  pulley,  set  in  a  bearing,  is  brought  into  rotary 
motion.  The  upper' end  of  the  shaft  b  being  coupled  by  a  pin  with  the 


; 


FIG.  343. 

hub  of  the  balance-wheel  c,  the  latter  is  likewise  set  rotating.  This 
fly-wheel  has  a  ball  bearing  with  an  adjusting  device,  disposed  eccentri- 
cally to  the  axis  of  the  fly-wheel.  In  the  fly-wheel  there  is  a  counter- 
weight, d  which  may  be  transposed  by  means  of  a  screw.  The  hub  of 
the  fly-wheel,  serving  as  journal  during  the  rotation  of  the  fly-wheel  at 
the  same  time,  is  set  in  the  bearing  of  the  frame  a,  which  is  also  coupled 


364 


FLOUR   MILLING 


[CHAP,  v 
The  sifter 


with  a  cross-head  carrying  the  footstep  bearing  of  the  shaft  b. 
runs  at  the  rate  of  190  to  200  revolutions  per  minute. 

The  number  of  sieves  is  twelve  ;  the  travel  of  the  product  is  shown 
clearly  enough.  The  cleaning  of  the  sieves  is  performed  by  means  of 
brushes,  which  act  in  the  manner  described  on  p.  352,  Fig.  326.  A 
perspective  view  of  the  Seek  Bros.  sifter£is  shown  on  Fig.  341. 


FIG.  344. 

After  Konegen's  sifters  were  put  on  the  market,  two-box  sifters  were 
also  constructed  by  other  makers. 

The  mounting  of  two-box  sifters  is  the  same  at  almost  all  European 
works.  The  mounting  by  G.  Daverio's  works  differs  to  a  more  or  less 
extent,  the  perimeter  of  the  supports  of  their  rods  lying  between 
the  boxes.  A  perspective  view  of  G.  Daverio's  sifter  is  given  in 
Fig.  342.  Fig.  343  represents  Dobrovy  and  Nabholtz's  one-box  sifter  with 
a  friction  drive  and  four  exterior  conveyers  for  the  shakers  Fig 
344  represents  G.  Luther's  two-box  sifter  on  cane  supports 


CHAP,  v]  FLOUR   MILLING  365 

3.  Dynamics  of  Plansifters 

Before  passing  to  a  further  description  of  the  construction  of  sifters, 
it  is  necessary  to  mention  several  considerations  concerning  favourable 
conditions  of  motion  for  sifters  of  different  types. 

We  are  given  a  single-box  sifter  (Fig.  345),  the  motion  of  which 
generates  a  centrifugal  force  of  every  point  of  it  round  its  axis  of  rotation. 
The  centrifugal  forces  of  each  point  of  the  sifter  being  parallel  at  any 
particular  moment  of  the  motion,  they  may  be  summed  up  after  the  law 
of  parallel  forces,  and  give  us  the  resultant  F  applied  in  the  centre  of 
gravity  0  of  the  sifter.  The  force  F  gives  the  moment  Fa  in  respect  to 
the  plane,  which  is  perpendicular  to  the  axis  of  the  bearing  c2.  To  pre- 
vent any  fracture  of  the  shaft  in  the  bearing  c2  or 
excessive  thickening  of  it,  it  is  necessary  to  set  a 
counterweight  on  the  shaft,  which  would  give  an 
equal  and  directly  opposite  moment  in  respect 
to  the  same  plane  of  the  bearing  c2.  The  counter- 
weight is  generally  made  in  the  shape  of  a  balance- 
wheel  with  stationary  and  adjustable  weights,  as  we 

have  seen  in  the  construction  of  Konegen's  sifter  or 

,  Q     ,  FIG.  345. 

that  ot  beck. 

Thus,  if  the  weight  in  the  balance-wheel  gives  a  centrifugal  force  N, 
when  rotating,  then  the  condition  from  which  this  force  is  defined  will  be  : 

Fa=Nb,  whence  we  define  N=FT. 

o 

But  since  a  >  b,  the  centrifugal  force  N  of  the  balance-wheel  must  be 
greater  than  the  centrifugal  force  F  of  the  sifter. 

Having  fitted  the  counterweight,  we  obtain  two  forces,  F  and  N9 
which  have  a  tendency  to  turn  the  axis  of  rotation  cc2  about  the  hori- 
zontal axis.  From  turning  to  the  right,  the  position  of  the  forces  being 
as  given,  the  axis  of  rotation  is  kept  by  the  reaction  X  of  the  bearing. 
The  value  of  X  will  be  defined,  if  we  take  the  moments  of  all  the  active 
forces  in  respect  to  the  point  c  ; 

Xa=N(a-b). 

Having  N=F^  and  on  defining  X  from  the  preceding  equation 
through  F,  we  obtain  : 


.  ..  . 

The  force  X,  with  such  a  construction  of  counterbalancing  the  centri- 


366 


FLOUR   MILLING 


[CHAP,  v 


fugal  force  of  the  sifter,  will  always  be  present.  Its  direction  alters  with 
the  motion  of  the  sifter  for  each  position,  which  imparts  great  vibration 
to  the  building.  Besides  that,  sifters  of  this  type,  producing  a  very 
considerable  moment  of  force  F  of  the  point  c1?  require  a  driving  journal 
of  large  size,  which  owing  to  the  great  pressure  of  the  journal  upon  the 
bearing  e  leads  to  a  rapid  wear  of  its  bush. 

Taking  all  that  into  consideration,  it  became  necessary  to  invent  a 
method  of  balancing  the  centrifugal  forces  of  the  sifter,  where  X  would 
be  equal  to  nought.  Since  X  will  be  equal  to  nought  if  a=b,  Engineer 
Konegen,  taking  these  considerations  as  basis,  offered  the  construction 
of  a  two-box  sifter,  shown  diagrammatically  in  Fig.  346.  In  this  draw- 
ing we  see  that  a  =b  when  the  centre  of  gravity  of  the  sifter  boxes  and  the 
counterweight  of  the  balance-wheel  lie  in  one  horizontal  plane. 

Machines  made  in  accordance  with  Konegen's  diagram  give  a  perfectly 


FIG.  346. 


FIG.  347. 


well-balanced  run  and  do  not  require  a  journal  of  so  great  a  size  as  the 
one  employed  in  Haggenmacher's  arrangement. 

An  unsound  idea  for  a  two  -box  sifter  is  suggested  by  Biihler's 
works  in  Uzwil,  which  places  the  fly-wheel  with  a  counterweight  lower 
than  the  boxes  (Fig.  347).  But  by  setting  a  second  fly-wheel  with  an 
inverse  counterweight  at  c2,  it  attains  the  annulment  of  the  injurious 
force  X.  For  defining  the  centrifugal  forces  R  and  T  of  these  two  fly- 
wheels, the  a  and  b  given,  i.e.  with  position  of  the  fly-wheels  to  be  found, 
we  have  : 

R  =  2F  +  T          .         .         ...      (2). 

And  taking  the  moments  2F  and  T  in  respect  to  the  point  cl5  we 
obtain  : 

Tb     .         .         .      ';:.-       ,J-      .      (3). 


Out  of  (3)  we  define  T=~,  and  out  of  (2)  we  obtain  jg= 


The  same  plan  for  cancelling  the  force  X  might  be  adapted  to  the 
single-box  sifter,  and  it  has  been  done  by  American   engineers  before 


CHAP.    V] 


FLOUR    MILLING 


367 


Biihler,  as  we  shall  see  below.  The  necessity  of  making  the  journal 
excessively  large,  owing  to  the  heavy  pressure  on  it  (the  moment  2Fa  is 
very  great),  does  not  allow  Biihler's  works  to  construct  sifters  with  a 
large  number  of  trays,  as  in  sifters  of  Konegen's  type.  Therefore  the 
largest  number  of  trays  in  these  sifters  does  not  exceed  seven. 

As  it  was  mentioned  just  now,  the  idea  of  balancing  the  Biihler  sifter 
has  been  borrowed  from  the  Americans,  but  it  turned  out  just  as  badly 
as  the  borrowing  of  the  idea  of  the  two-box  sifter  from  Konegen.  The 
American  engineers  place  the  second  fly-wheel  (Fig.  347)  higher  than  the 
box  of  the  sifter,  and  balance  the  pressure  caused  by  the  centrifugal  force 
2F  on  two  fingers  e.  Such  an  arrangement  of  the  balance-wheels  gives 
their  centrifugal  forces  K>1=F  and  2F  in  the  total,  whereas  in  Biihler's 


5 


*  — *  r~ • - T 

7   :  I  e  i- 

k,.J  D...J 

«-,  *  »  v  A 


FIG.  348. 

diagram  R  is  always  larger  than  2F,  and  is  equal  to  2F  only  when  b  is 
infinitely  large,  which  is,  of  course,  impossible. 

In  drawing  an  inference  from  the  above  considerations,  we  must  agree 
that  the  best,  perfectly  balanced  makes  of  sifters  are  shown  in  the 
two-box  diagram  of  the  type  illustrated  in  Fig.  346,  after  which  comes 
the  American  diagram  in  Fig.  347,  which  allows  the  spaces  A  to  be 
utilised,  wasted  by  Biihler,  owing  to  the  idea  of  Konegen's  two-box  sifter 
being  misunderstood. 

The  use  of  the  single-box  sifters  (Fig.  345)  can  be  justified  only  by 
their  extreme  cheapness,  because  these  sifters  shake  the  mill  buildings 
greatly,  when  disposed  in  the  manner  accepted  by  our  builders. 

These  machines  being  still  erected  in  mills,  it  is  necessary  to  point  out 
the  best  way  of  erecting  them  in  the  buildings. 

The  sifters  are  generally  arranged  lengthways  by  the  plan  of  the  floor 
which  is  necessitated  by  the  longitudinal  disposition  of  the  roller  mills 
(Fig.  348).  To  reduce  the  vibration  of  the  mill  by  the  forces  X,  there 


368  FLOUR    MILLING  [CHAP,  v 

must  be  an  even  number  of  sifters.  In  our  diagram  there  are  four,  and 
they  run  in  pairs  to  the  right  and  to  the  left.  But  this  to  a  certain 
extent  involves  a  longitudinal  vibration  of  the  mill,  since  the  forces  X 
longitudinally  disposed  in  opposite  directions  at  the  moment  of  the 
greatest  longitudinal  declination  of  the  sifters  cause  the  contraction  or 
extension  of  the  floor,  the  resistancy  of  which  is  sufficiently  great. 

At  the  moment  of  the  greatest  transversal  deflection  of  the  sifters 
the  forces  X  act  in  one  direction  and  tend  to  upset  the  building.  If  the 
run  of  the  sifters  is  so  set  that  the  sifters  1  and  2  give  the  greatest  declen- 
sion to  the  wall  CD,  and  the  sifters  3  and  4  to  the  wall  AB,  a  moment  of 
forces  2X,  twisting  the  building,  is  obtained.  It  is  possible  to  plant  four 
sifters  so  that  the  forces  X  of  the  transversal  direction  would  also  give 
alternately  a  contraction  and  an  extension  of  the  floor.  That  would  be 
possible  with  a  great  number  of  sifters.  However,  even  if  this  were  suc- 
cessfully done,  once  started,  the  sifters  would  soon  be  thrown  off  their 
run,  for  the  unequal  slipping  of  the  belts  on  all  the  sifters  alters  the 
number  of  revolutions.  Hence  the  shocks  imparted  to  the  building 
are  unequal  in  force,  and  attain  the  widest  limits  after  unequal  periods  of 
time. 

The  only  means  of  combating  the  vibration  of  the  mill  building, 
which  leads  to  frequent  repairs,  and  even  to  its  ruin,  is  to  throw  out  the 
single-box  non-balanced  sifters  and  replace  them  by  two-box  ones. 

Another  phenomenon  when  the  run  of  the  sifter  loses  its  evenness,  is 
called  "  wandering."  The  wandering  generally  takes  place  at  the  starting 
of  the  sifter,  and  when  it  has  once  begun  it  may  gain  in  power  until  the 
stands  or  the  drop-hanger  frames  of  the  sifter  break.  This  phenomenon 
has  its  origin  in  the  fact  that  the  sifter  being  started,  the  force  of  friction 
of  the  pin  in  the  bearing  tends  to  turn  the  box  round  the  axis  of  the 
pin  in  the  direction  opposite  to  the  rotation  of  the  finger. 

To  make  that  clear  (Fig.  349),  we  shall  take  the  points  where  the 
supports  or  the  suspension  rods  are  fixed,  1  (left-hand  side)  and  2  (right- 
hand  side).  With  the  normal  motion  of  the  sifter  the  point  1  or  2  must 
travel  in  the  circle  K.  But  if  the  sifter  has  a  tendency  to  turn  round  the 
axis  of  the  finger  in  a  circle  M ,  the  point  passes  into  position  I1,  so  that  its 
trajectory  of  motion  acquires  an  elliptic  form  L.  At  the  same  time  the 
point  2  moves  to  point  21  and  gives  a  trajectory  L1— a  compressed  circle. 
The  nearer  to  the  axis  of  the  finger,  the  less  is  the  deflection  from  the 
circular  motion,  and  the  point  3,  being  in  contact  with  the  finger,  has  no 
deflection  from  the  normal  circular  motion  K.  Hence  it  is  clear  that  in 
the  stands  or  drop-hangers  1-1  the  wandering  causes  an  extending 


CHAP.    V] 


FLOUR    MILLING 


369 


deformation  and  a  contracting  deformation  in  the  stands  2-2.  And  if 
the  forces  causing  the  tensions  are  sufficiently  great  they  may  lead  to 
breakage. 

To  avoid  this  constructive  defect  some  of  the  works  suggest  various 
means  of  communicating  a  rigidness  to  the  system  joining  the  supports 
and  the  boxes  of  the  sifters. 

Since  it  is  necessary  that  the  supports  should  be  parallel  during  the 
operation  of  the  sifters,  attempts  are  made  to  hold  them  in  that  position 
by  supplementary  kinematic  junctions. 

One  such  device  is  shown  on  Fig.  350.  The  two-box  sifter  illus- 
trated is  set  on  four  supports  a  of  an  ordinary  construction.  On 
the  foundation  frame  v  there  is  set  a  shaft  b  which  can  rotate  in 
bearings  r.  At  the  ends  of  the  shaft  are  set  rods  c1  and  c2,  the  ends  of 


•K      K 


I1 


V  ?' 


K 


r 

\  ^ 


FIG.  349. 


FIG.  350. 


which,  3  and  4,  are  connected  by  Hooke's  joints  or  a  spherical  journal 
with  rods  dld?  attached  likewise  with  joints  to  the  frame  of  the  sifter  at 
the  points  1  and  2.  It  is  quite  evident  that  the  supplementary  stands 
make  the  frame  more  rigid,  and  form  no  obstacle  to  the  gyratory  pro- 
gressive motion  of  the  sifter.  In  this  system  the  shaf  tb  could  have  been 
placed  on  the  lower  part  of  the  box,  and  then  the  kinematic  junction 
b-c-d  would  be  reversed  in  respect  to  the  plan  given.  These  supple- 
mentary junctions  may  be  also  fixed  to  suspended  sifters. 

Another  construction  of  the  junctions  is  illustrated  in  Fig.  351.  The 
top  ends  of  the  system  cl-b-cz  here  have  circular  discs  /l-,/2,  which  glide 
between  two  guide-plates  g^-g*  attached  to  the  boxes  of  the  sifter.  The 
system  cMj-c2  being  perfectly  rigid,  the  centre  line  of  the  discs  is  always 
parallel  to  the  shaft  b.  When  the  sifter  is  in  rotation  the  discs  will  be 
running  up  and  down,  to  the  right  and  to  the  left  (components  of  motion). 

therefore  wandering  is  here  impossible. 

2A 


370 


FLOUR    MILLING 


[CHAP,  v 


A  third  method  (Fig.  352)  gives  the  system  n^-b-n1,  the  ends  of  the 
levers  h1  and  n2  being  joined  fast  to  the  foundation  supports  a1  and  a2. 
A  detail  of  these  junctions  is  to  be  seen  in  Fig.  353. 

A  variation  of  the  third  method,  where  the  diagonally  set  stands  are 
joined  and  not  the  side  ones,  is  shown  on  Fig.  354. 

Of  all   the  systems  examined,  only  the  second  prevents  wandering 


FIG.  351. 


c*' 


FIG.  352. 


(Fig.  351).  The  two  other  systems  do  not  give  absolute  regularity,  and 
they  therefore  should  be  displaced  in  the  models  offered  by  some  of 
the  European  works,  which  are  mostly  variations  of  the  second  method 
(Biihler  Bros,  and  Kapler). 

The  problem  of  preventing  the  tendency  to  wander  has  been  perfectly, 
correctly,  and  expediently,  from  the  constructive  point  of  view,  solved 
by  the  American  works  and  by  Thos.  Robinson's  works  in  England. 


FIG.  353. 


FIG    354. 


We  shall  first  examine  the  American  method. 

Fig.  355  illustrates  the  transmission  of  motion  to  the  box  of  the  sifter 
evolved  by  the  I.  Schultz  O'Neile  Co.  of  Minneapolis.  The  toothed 
gearing  to  the  shaft  4  is  set  in  the  main  frame,  to  which  a  cross-head  7  is 
bolted.  On  the  cross-head  there  are  set  adjustable  bearings,  a  detail  of 
which  is  shown  on  C,  for  two  rods  14  with  rolls  15  freely  set  on  them. 
These  rolls  enter  into  the  guiding  cross-head  and  slippers  17  bolted  to 


CHAP.    V] 


FLOUR    MILLING 


371 


the  frame.  The  shaft  4  is  joined  fast  to  the  cross -head  24,  into  which  the 
driving  pin  set  in  the  lower  part  of  the  sifter  box  enters.  To  the  same 
cross-head,  with  bolts  0  having  a  spring  thrust,  is  attached  a  counter- 
weight 25,  which  may  be  brought  closer  or  farther  with  the  aid  of  nuts  a. 
When  the  sifter  is  set  in  motion,  its  box  performs  a  gyratory  progressive 
motion,  which  is  composed  of 
the  motion  of  the  rolls  to  the 
right  and  to  the  left,  and  of 
that  of  the  guiding  slippers  17 
backwards  and  forwards. 

Fig.  D  shows  the  construc- 
tion for  large  sifters.  In  this 
wise,  here  we  find  adapted 
the  principle  examined  in  Fig. 
351. 

It  is  difficult  to  judge  of 
the  rigidity  of  this  machine 
or  of  its  efficiency,  since  the 
sifters  have  made  their  appear- 
ance on  the  market  but  lately. 

The  problem  of  obviating 
any  wandering  was  solved  in 
the  most  expedient  manner  by 
the  American  engineers,  who 
first  suggested  adapting  two 
driving  pins. 

Figs.  356  and  357  illustrate 
the  method  of  transmitting 
the  motion  to  A.  Wolf's  sifter, 
eliminating  all  possibility  of 
wandering.  The  box  of  the 
sifter  is  supported  on  four  stands 
B.  The  driving  pins  /  of  the 
fly-wheels  freely  enter  into  the  hubs  d,  which  are  adjusted  by  means  of 
bolts  d1.  The  balance-wheels  F  with  the  counterweights  are  brought  into 
rotation  from  the  belt-pulley  S  with  the  aid  of  toothed  gears  h-hl.  To 
impart  a  greater  smoothness  to  the  run  a  belt  g  is  set  on  the  fly-wheels  F. 
In  this  construction  the  turning  of  the  sifter  round  its  axis,  i,e.  the 
wandering  motion,  is  impossible. 

Of  the  European  works,  that  of  Thos.  Robinson  in  England  constructs 


FIG.  355. 


372 


FLOUR    MILLING 


[CHAP,  v 


the  transmission  of  motion  on  the  same  principle,  i.e.  with  the  aid  of 
two  cranks.     On  Fig.  358  we  have  a  diagrammatic  illustration  of  the 


IT  ITU 


FIG.  356. 


FIG.  357. 


transmission  in  Th.  Robinson's  two-box  sifter  of  the  latest  type.     The 
boxes  A  are   joined   together  by  H -irons   1.     The  cranks  4  are  fixed 


FIG.  358. 


in  plates  5  joined  to  the  H -irons  and  cross-bars  6.  The  balance-wheels 
2  with  counterweights  are  brought  into  motion  by  one  common  belt  3, 
running  over  the  driving  pulley  8  and  the  jockeys  7-71.  The  jockey  7 


CHAP,   v] 


FLOUR   MILLING 


373 


at  the  same  time  serves  as  a  belt  tightener.  The  frame  of  the 
bearing  holding  this  jockey  is  set  in  the  guiding  cross-head  and  slippers 
and  joined  by  lever -joints  1 1-12-1  lj,  the  last  of  which  has  an  adjust- 
able weight  Q.  By  moving  it  to  the  right  or  to  the  left,  we  may 


slacken  or  tighten  the  belt.     A  perspective  view  of  the  sifter  is  shown 
in  Fig.  359. 

The  drive  evolved  by  Thos.  Robinson  is  decidedly  superior  to  that  of 
A.  Wolf,  as  it  discards  the  rigid  and  uneconomical  tooth  gearing.  But 
Wolf's  drive  is  better  in  so  far  that  each  balance-wheel  has  an  independent 


374  FLOUR   MILLING  [CHAP,  v 

gearing.  However,  both  the  drives  should  be  absolutely  accurate.  In 
Th.  Robinson's  drive  there  must  be  a  great  accuracy  in  the  equality  of 
diameters  of  the  fly-wheels,  otherwise,  even  with  the  difference  of  1  mm. 
in  the  diameters,  the  belt  will  acquire  a  strong  slipping  motion  on  the 
smaller  pulley,  which  will  cause  a  rapid  wear  of  the  belt. 

In  our  opinion  Robinson's  construction  might  be  improved  by  throw- 
ing the  belt  off  one  of  the  pulleys  and  connecting  the  driving  cranks  by  a 
coupling  rod.  In  this  way  even  a  considerable  difference  in  diameters 
of  the  fly-wheels  would  be  of  no  consequence. 

Thus,  making  an  estimate  of  the  types  of  sifters  from  the  point  of 
view  of  dynamics,  we  must  give  preference  to  two -box  sifters,  to  such 
types  besides,  which  have  the  balance-wheel  with  the  counterweight  set 
between  the  boxes,  and  the  distance  between  the  horizontal  planes  of 
the  centre  of  gravity  of  the  sifter  and  of  the  balance-wheel  equal  to 
nought  or  very  small. 

In  selecting  sifters  with  mechanisms  preventing  wandering,  those 
should  be  chosen  where  this  is  effected  by  means  of  two  driving  cranks 
which  absolutely  prevents  running  off. 


4.  American  Sifters 

In  the  development  of  sifter  construction,  just  as  in  the  building 
of  roller  mills,  the  Americans  chose  a  route  totally  different  to  that  of 
the  Europeans.  A  characteristic  peculiarity  of  their  sifters  is  the  inclined, 
zigzag-shaped  arrangement  of  the  sieves.  Having  observed  the  inequi- 
librium  of  motion  in  the  single-box  sifters  with  one  counterweight,  the 
American  engineers  were  the  first  to  solve  the  problem  of  equilibrium. 
The  first  (A.  Wolf's)  type,  designed  to  obviate  the  running  off  of  the 
sifter  during  operation,  also  belongs  to  the  Americans. 

These  considerations,  as  well  as  the  ignorance  not  only  of  the  Russian 
but  of  the  European  technicians  too,  of  the  constructions  of  American 
sifters,1  induced  us  to  devote  a  separate  chapter  to  them. 

Noye's  Zigzag  Sifter.— Figs.  360  and  361  show  us  the  longitudinal 
section  and  the  perspective  view  of  Noye's  sifter.  The  box  of  the  sifter 
consists  of  two  divisions  for  sieves,  between  which  there  passes  the 
driving  crank-shaft  v  carrying  two  hand-wheels  with  counterweights  q. 
These  counterweights  may  be  moved  closer  to  or  further  from  the  axis 
of  rotation  by  means  of  a  screw  r.  The  lower  hand-wheel  is  cast  in  one 

1  Only  in  Pappenheim's  work  is  there  a  general  description  of  the  sifter  built  by  the  works 
of  Nordyke  &  Marmon  Co. 


CHAP.    V] 


FLOtm   MILLING 


375 


piece  with  the  driving  belt-pulley  s.  The  shaft  rests  on  the  step-bearing 
t  and  is  held  in  a  vertical  position  by  two  bearings  o  set  in  the  cross-bars 
of  the  frame  A.  The  bearing  p  driven  by  a  crank  shaft  is  fixed  in  the 
bottom  of  the  sifter  box,  which  is  suspended  on  four  rods  a  with  ball 
bearings.  The  product  is  fed  in  through  S  and  falls  on  the  sieve  1,  which 
delivers  its  overtails  (break  semolina,  middlings,  or  bran)  through  the  spout 
s1?  while  the  throughs  drop  on  to  the  cloth  11?  which  passes  it  to  the  sieve 
2.  The  sieve  2  has  the  large  tailings  discharged  from  the  sifter  and  passes 
the  throughs  to  the  sieve  3,  which,  together  with  the  tails  of  the  sieve  4, 
carries  the  product  to  the  last  sieve  5.  The  throughs  from  the  sieve  4  are 
sent  out  of  the  sifter  by  the  cloth  4X  together  with  the  throughs  of  the  sieve 
5  by  means  of  the  cloths  5t.  Thus  the  sieves  3,  4,  and  5  yield  flour  as 


FIG.  360. 


FIG.  361. 


throughs  into  the  spout  /,  the  sieve  5  in  its  lower  part  gives  dunst  as 
throughs  to  the  spout  //,  the  sieve  1  large  tailings  into  spout  ///,  and  the 
sieves  2,  5,  and  the  cloth  6j  tailings  of  mixed  middlings  into  the  spout  IV. 

The  cleaning  of  the  sieves  is  performed  by  brushes  brought  into 
operation  by  a  rather  complicated  device.  On  the  wires  c  thrown  across 
the  guides  b,  there  are  fixed  the  brushes  /,  which  run  under  the  sieve  for- 
wards and  backwards.  The  wire  tracking  c  after  the  guides  b,  doubling 
over  the  idlers  d,  all  join  together  at  c  with  the  chain  of  the  gearing, 
which  is  brought  into  operation  from  the  shaft  v  by  the  pulleys  7-8  and 
by  the  conic  toothed  gear  n.  To  prevent  the  flour  from  escaping,  the 
openings  in  the  box  for  wire  tracking  are  covered  with  casings  B.  For 
guiding  the  driving  belt  there  are  the  loose  pulleys  D. 

Nordyke  &  Harmon  Co.'s  Sifters.  —  The  balanced  two-box  sifter 
from  the  Nordyke  &  Marmon  Co.  works,  with  a  zigzag  arrangement  of 


376 


FLOUR   MILLING 


the  sieves,  is  shown  in  Figs.  362  and  363.  The  boxes  A  are  joined  to 
their  foundation  frames  by  cast-iron  parallel  guides  /  and  cross-heads  T, 
in  which  the  bearings  of  the  driving  shaft  V  are  fixed.  The  boxes  are 
suspended  on  four  cane  rods  E  :  Mis  the  driving  belt  pulley,  0  the  guid- 
ing loose  belt-pulleys,  which  are  fixed  on  brackets  Q  adjusted  by  means 


FIG.  363. 


of  screws  G.  Above  and  below  the  boxes  there  are  counterweights  8  set 
on  the  shaft  V:  H  and  E  are  the  oil  boxes  feeding  the  top  and  the  bottom 
belt-pulleys.  The  rods  are  fixed  to  the  thick  ceiling  board  J,  set 
across  the  ceiling  beams  K. 

A  longitudinal  section  of  the  sifter  box  is  given  in  Fig.  364.  The 
bolting  trays  1,  2,  3,  4,  and  5  are  arranged  in  zigzag  manner  with  different 
inclines  according  to  the  size  of  the  product,  the  greater  incline  corre- 


n: 


FIG.  364. 


FIG.  365. 


spending  to  the  first  sieve,  which  bolts  the  coarser  product.  Owing  to  the 
different  inclination  of  the  sieves,  we  obtain  correspondingly  different 
velocities  of  motion  of  the  product  treated.  This  very  important  con- 
dition of  an  even  sifting  of  the  coarse  and  fine  product  is  not  taken  into 
consideration  by  European  engineers.  For  feeding  the  throughs  to  the 
following  sieves  there  are  the  inclined  timber  plates  11?  2X  ,3,,  4j  and  5j. 
The  sieves  are  cleaned  by  means  of  brushes  a. 


CHAP,  v]  FLOUR   MILLING  377 

Into  the  box  of  the  sifter,  through  the  side,  are  inserted  the  bolting 
trays,  the  perspective  view  of  which  is  illustrated  in  Fig.  365,  and  in 
section  in  Fig.  366,  where  it  may  be  seen  that  each  tray  is  clothed  with  a 
working  sieve  on  the  upper  side,  and  an  open  wire  tissue  for  the  brushes 
from  below.  The  tray  is  divided  by  transversal  timber  cross-pieces  a  to 
limit  the  area  of  operation  of  the  brushes  and  to  prevent  their  meeting. 

An  ordinary  arrangement  of  counterweights  is  shown  in  Fig.  367 
(the  -bottom  counterweight),  which  likewise  gives  an  idea  of  the  trans- 
mission of  motion  to  the  boxes.  The  cast-iron  belt-pulley  has  a  large 
hub  B  in  which  there  is  an  adjustable  bearing  A  for  the  shaft.  This 
bearing  is  adjusted  by  means  of  a  set  screw  on  one  side  and  a  tension 
spring  D.  The  counterweight  E  can  be  moved  in  the  guiding  parallels  by 


FIG.  366.  FIG.  367. 

turning  the  set  screw  F.  In  the  counterweight  there  are  cylindric  holes, 
in  which  in  case  of  need  the  supplementary  weights  G  are  put,  and  fixed 
from  below  by  bolts  passing  through  holes  in  them. 

Sifters  made  at  Wolfs  Works.— We  have  already  partly  become  ac- 
quainted with  one  of  the  makes  of  Wolf's  sifters.  Figs.  368  and 
369  represent  a  longitudinal  and  a  cross-section  of  one  half  of  the  sifter, 
operating  for  two  products.  In  this  sifter,  as  almost  in  all  American 
types,  the  sieves  are  set  in  a  zigzag  line.  The  sieves  are  placed  into 
the  box  from  the  side,  and  held  by  means  of  cast-iron  planks  a  fastened 
by  thumb-screws  b.  The  motion  is  communicated  to  the  sifter,  as  we  have 
seen  earlier  (p.  372,  Fig.  358),  by  means  of  two  driving  cranks  and  balance- 
wheels  with  counterweights  brought  into  rotation  by  conic  toothed  gears. 
The  number  of  bolting  trays,  five,  is  the  same  as  in  the  preceding  construc- 
tion, with  a  similar  flow  of  the  product. 

This  sifter  does  not  wander,  but  its  run  is  not  balanced,  therefore 


378 


FLOUR   MILLING 


[CHAP,  v 

the  vibration  (force  X,  p.  366,  Fig.  347)  of  the  shafts  v,  communicated 
to  the  floor  through  the  bearings  d,  tends  to  shake  the  mill. 

A  section  of  Wolfs  balanced  sifter  is  shown  in  Fig.  370,  and  its  dif- 


FIG.  368. 


FIG.  369. 


ferent  parts  and  disposition  of  sieves  are  shown  in  Figs.  371,  372,  and  373. 
The  drawing  of  Fig.  370  shows  us  that  the  counterweight  Q  is  set  inside  the 
box  A,  so  that  its  centre  of  gravity  lies  in  the  plane  of  the  centre  of  gravity 
of  the  box.  The  crank-shaft  is  not  made  in  one  whole  piece,  but  con- 
sists of  two  parts,  v  and  vlt  con- 
nected by  joints  at  o.  The  top 
part  of  the  shaft  rotates  in  ball 
and  socket  bearings  of  the  cross- 
heads  b  connected  with  the  box 
of  the  sifter  as  shown  in  Fig.  372. 
Owing  to  a  special  construction 
of  the  junction  at  o,  the  sifter 
can  fluctuate  in  the  inclined  plane, 
passing  from  position  1-1  to  2-2. 
Let  us  examine  more  minutely 
the  driving  mechanism  shown  in 
Fig.  371. 

The  lower  part  of  the  shaft  v 
is  set  on  a  ball  collar  thrust  bear- 
ing a  and  held  in  a  vertical  position  by  two  ball  bearings  c.   On  the  top  part 
of  the  shaft  v  there  is  set  a  split  belt-pulley  S  on  the  hub  P  of  the  cup  T. 
The  upper  crank  part  of  the  shaft  v1  has  at  its  lower  end  a  cavity  for  the 


FIG.  370. 


FLOUR    MILLING 


379 


CHAP.    V] 

finger  of  the  ball  bearing  o,  which  enters  into  the  steel  shoe  of  the  top  end 
of  the  shaft  v.  The  inner  arms  of  the  cup  T  and  the  cross-head  ra  fixed  to 
the  end  of  the  shaft  vl  form  a  cross -head  coupling  of  the  shafts  v  and  vlt 
resembling  the  junction  of  driving  irons  in  stone  mills,  owing  to  which  the 
rotation  of  v  is  communicated  to  v1?  and  consequently  to  the  sifter.  The 


FIG.  371. 

shaft  v±  is  also  held  in  two  ball  and  socket  bearings.  The  counterweight 
Q  is  bolted  to  the  shaft  by  bolts  n  :  such  fixing  of  the  counterweight 
allows  of  easily  raising  or  dropping  it  when  necessary.  By  means  of 
cross-heads  b  and  set  squares  d  the  whole  system  is  coupled  with  the  box 
of  the  sifter.  This  balancing  arrangement  totally  obviates  the  possibility 
of  vibration,  since  the  centrifugal  forces  of  the  sifter  box  and  the 
counterweight  run  in  one  plane. 


3SO 


FLOUR   MILLING 


In  Fig.  372  is  shown  a  horizontal  section  of  the  sifter  box 
above  the  counterweight.  The  sifter  can  bolt  four  or  eight  distinct 
products  ;  in  the  latter  case  the  sifter  is  divided  into  two 
floors. 

The  box  is  suspended  on  brackets  k  for  the  cane  rods.  The  wire 
sieves  are  cleaned  by  means  of  heavy  tappers  t,  and  the  silk  ones 


FIG.  372. 


by  thin  steel  chains  p  attached  with  their  ends  to  the  frame  of  the 
sieve. 

A  longitudinal  section  of  the  sifter  is  shown  in  Fig.  373.  Here  one 
part  of  the  sieves  is  given  in  longitudinal  section,  and  one  in  cross-section. 
The  sifter  we  are  examining  is  built  for  eight  products,  i.e.  each  section 
operates  independently  for  two  products.  For  each  product  there  are 
six  bolting  trays,  every  one  of  which  has  its  own  cloth.  The  tray  1  gives 


CHAP.    V] 


FLOUR    MILLING 


381 


break  I  as  tails,  the  tray  2  middlings  //,  trays  3,  4,  and  5  yield  flour  as 
throughs,  and  the   sixth  tails  over   fine    middlings  and  gives  dunst  as 


FIG.  373 


throughs.     The-  lower  floor  of  the  first  section  differs  in  that  the  second 
semolina  tray  is  substituted  by  one  for  flour. 

This  sifter  serves   for   a   mill  having  four  breaks  and  four  reduc- 
tions. 


382 


FLOUR   MILLING 


[CHAP,  v 


5.  Free  Swinging  Plansifters 

As  we  have  seen  already,  both  the  single  and  the  double  box  sifters 
have  one  sole  defect  from  the  point  of  view  of  their  dynamics.  They 
both  wander,  i.e.  tend  to  revolve  round  the  axis  of  the  crank,  particularly 
so  at  the  start.  However,  this  fault- has  been  also  obviated  by  the  con- 
structors at  Robinson's  in  England,  and  Wolf's  in  America,  with  the  aid 
of  two  driving  cranks. 

Thus,  from  the  standpoint  of  dynamics,  the  sifter  is  a  quite  perfect 
machine  at  the  present  moment.  But  now  a  new  problem  has  presented 


•x 


FIG.  374. 


FIG.  375. 


itself  to  the  engineers — to  simplify  the  relatively  complex  and  heavy 
details,  of  which  the  crank  driving  the  sifter-boxes  and  the  balance- 
wheel  with  the  counterweight  are  considered  to  be  the  parts  most  open 
to  criticism. 

This  question  was  worked  at  by  American  and  European  constructors, 
and  finally,  at  the  end  of  1911,  there  appeared  several  patents,  first  in 
America  and  then  in  Europe,  for  so-called  "  self-balancing  "  sifters. 

Before  giving  an  estimate  of  these  sifters  from  the  point  of  view  of 
dynamics  and  of  other  circumstances  characterising  the  merits  and  defects 
of  the  new  machines,  we  ought  to  make  the  student  acquainted  with  their 
construction. 

The  classification  of  the  new  machines  must  be  based  on  the  character 
of  the  driving  mechanism.  In  this  respect  there  are  known  two  kinds 


CHAP.    V] 


FLOUR    MILLING 


383 


of  drives,  rigid  '  and  flexible.     Both  types  of  construction  totally  obviate 
the  crank  method  of  obtaining  the  gyrating  rotary  motion. 

Fig.  374  illustrates  a  perspective  view  of  the  sifter  from  "  The  American 
Machinery  Co."  works,  which  brought  out  this  new  type  of  machine  as  early 
as  November  1911.  The  new  construction  is  a  two-box  sifter  suspended 
on  four  sets  of  canes  A .  It  is  brought  into  rotary  motion  by  the  shaft  B, 
which  is  coupled  to  the  sifter  and  the  driving  belt-pulley  as  shown  on 
Fig.  375.  The  steel  cross-head  G,  ending  in  a  hollow  finger  D,  couples 
the  sifter  boxes.  On  the  finger  there  is  loosely  fitted  the  bush  E,  to  the 
base  of  which  the  shaft  B 
is  joined,  by  means  of  a 
screwed-on  nut  a  covered  by 
a  box  washer  6.  This  bush 
carries  a  weight  F,  which 
rotates  freely  on  a  joint. 
The  top  end  of  the  shaft  is 
supported  by  a  ball  bearing 
0  entering  into  the  filbore  of 
the  drop -hanger  frame  K. 
The  belt-pulley  H  is  set  on 
the  shaft  B  so  that  its  centre 
line  lies  on  a  plane  with  the 
centre  of  rotation  of  the  ball 
bearing. 

When  starting  the  sifter  . 
the  belt-pulley  H  receives 
its  motion  from  the  driving-belt  and  brings  the  shaft  B  into  rotation. 
The  ball  bearing  G  glides  in  the  filbore  of  the  drop -hanger  frame.  At 
first  the  bush  E  glides  over  the  finger  D  without  bringing  the  sifter 
into  operation.  But  in  proportion  as  the  mtmber  of  revolutions 
increases,  the  weight  F  develops  a  centrifugal  force ;  it  rises  and  carries 
the  finger  D  aside  with  it. 

In  this  manner  the  gyrating  rotary  motion  of  the  sifter  is  obtained 
owing  to  the  centrifugal  force  of  the  weight  F.  This  system  of  driving 
the  sifter  we  call  "  rigid,"  to  distinguish  it  from  another  construction 
which  will  be  examined  later. 

After  the  type  of  the  American  sifter,  also  with  a  rigid  drive,  a  new 
construction  (Fig.  376)  has  recently  .been  evolved  by  the  works  of  Am  me, 
Giesecke,  and  Konegen  in  Brunswick. 

1  So  we  shall  conventionally  name  the  drive  from  a  rotating  shaft- 


FIG.  376. 


384 


FLOUR   MILLING 


[CHAP,  v 


The  idea  of  a  free  swinging  sifter  attracted  the  constructors  so  much 
that  almost  all  more  or  less  large  European  works,  one  after  the  other, 
began  supplying  the  market  with  machines  of  that  type.  One  may  say 
that  the  works  were  seized  by  an  epidemic  of  constructing  sifters  to  work 
on  the  principle  of  utilisation  of  the  centrifugal  force. 

The  works  "  Erste  Landwirtschaftliche  Maschinenfabrik,"  in  Buda- 
pest, and  those  of  J.  Prokop  in  Pardubitz,  Austria,  almost  simul- 
taneously put  on  the  market  free  swinging  sifters  with  flexible  drives. 
Besides  that  several  patents  more  were  claimed  for  similar  sifters,  of 
which  the  most  typical  in  its  idea  is  Karl  Gillesheimer's  construction, 

shown  in  Fig.  377. 

The  essence  of  the  con- 
struction of  Gillesheimer's 
sifter  consists  in  the  following. 
The  sifter  box  is  suspended 
on  four  rods  /.  The  fast 
pulley  d  is  made  to  rotate 
from  the  shaft  b  by  means  of 
the  belt-drive  a  guided  by  two 
jockeys  c,  fixed  on  the  box  of 
the  sifter.  The  belt-pulley  d 
is  set  on  the  shaft  g  to  which 
the  weight  n  is  fastened.  The 
shaft  g  rotates  in  bearings  h 
and  i  coupled  to  the  frame  e. 
An  important  part  of  the 
mechanism  is  the  friction 
coupling.  The  top  part  k  of  the  friction  clutch  is  keyed  on  the  shaft, 
and  the  bottom  part  is  formed  by  the  belt-pulley  d  freely  rotating 
on  the  shaft  g.  On  the  upper  end  of  this  shaft  is  fitted  a  spring  I, 
the  tension  of  which  is  adjusted  by  a  nut  ra.  By  altering  the  tension 
of  the  spring,  the  pressure  of  the  friction  disc  1c  can  be  altered,  owing 
to  which  the  force  of  friction  of  the  clutch  alters,  and  a  modifica- 
tion in  the  magnitude  of  the  moment  rotating  the  box  is  thus  attained. 
When  started,  the  belt-pulley  d  at  first  glides  over  the  friction  disc  Ic, 
and  then  gradually  the  force  of  friction  forms  a  moment  of  sufficient 
magnitude,  which  brings  the  sifter  into  a  gyrating  rotary  motion,  and 
when  the  number  of  revolutions  reaches  the  normal  the  gliding  motion 
ceases.  According  to  the  inventor's  idea  the  friction  gear  must  at 
the  same  time  be  the  regulator  of  the  number  of  revolutions,  since,  in 


FIG.  377. 


CHAP.    V] 


FLOUR    MILLING 


385 


case  of  increase  or  decrease  of  the  number  of  revolutions  of  the  belt- 
pulley  d,  and  consequently  of  the  counterweight  n  as  well,  there  springs 
up  a  force  of  friction  between  the  disc  and  the  belt-pulley,  which  either 
acts  as  a  brake  (if  the  number  of  revolutions  increases),  or  drives  the 
pulley  d  along  with  it. 

The  Voll  and  Mertz  free  swinging  sifter  with  a  flexible  drive  is  given 
on  Fig.  378. 

The  gyratory  rotating  motion  of  Voll  and  Mertz's  sifter  is  based  on 
the  principle  we  have  already  examined.  The  weight  g  is  set  in  the  fly- 


Longitudinal  section  of  the  Sifter  through  AB. 


Cross  section  of  the  Sifter  through  CD. 


Plan  of  the  Sifter  without  Sifting  Trays. 
FIG.  378. 

wheel  a  in  the  same  manner  as  the  counterweight  is  set  in  the  crank  sifters. 
This  fly-wheel  is  fastened  on  the  shaft,  which  is  supported  by  a  ball-collar 
thrust-bearing  c  and  a  ball-bearing  d,  fixed  to  the  cross-bar  p  of  the  frame 
coupling  the  sifter  boxes.  On  the  same  shaft  as  the  fly-wheel  there  is 
set  the  receiving  belt -pulley  b  driven  by  means  of  a  belt,  which  is  carried 
to  this  pulley  by  means  of  jockeys  /  stationed  on  the  sifter  boxes. 

All  the  constructions  examined  show  that  the  gyrating  rotary  motion 
of  the  sifters  is  attained  owing  to  the  action  of  the  centrifugal  force, 
first  of  the  weight,  and  next  of  the  sifter  itself. 

Passing  by  a  more  minute  estimate  of  the  constructive  details  of  free 
swaging  sifters,  which,  doubtlessly,  will  be  still  more  perfected,  we  shall 


386  FLOUR   MILLING  [CHAP,  v 

direct  our  attention  to  the  fundamental  merits  of  the  new  machines, 
which  are  ascribed  to  them  by  their  inventors. 

1.  A  free  swinging  sifter  requires  no  bulky  setting  of  the  crank  shaft, 
which  makes  the  machine,  as  well  as  its  erection,  heavier,  more  expensive 
and  complex. 

2.  From  the  dynamic  standpoint  the  free  swinging  sifter  is  an  ideal 
machine,  giving  no  shocks  to  the  mill  building. 

As  concerns  the  first  point,  i.e.  the  simplification  and  reduction  of 
weight  of  the  construction,  this  may  be  acknowledged  as  true,  but  only 
to  a  certain  degree.  The  bulky  mounting  of  the  crank  shaft  is  indeed 
discarded,  but  the  rigid  as  well  as  the  flexible  drives  have  several  defects. 

Firstly,  the  American  rigid  drive  has  a  complex  ball  drop-hanger 
frame,  which  will  hold  the  oil  badly.  Also  its  belt-pulley  performs, 
besides  the  ordinary  rotatory,  a  conic  motion,  which  causes  unequal 
tension  of  the  edges  of  the  belt.  Secondly,  the  flexible  drive  is  far  from 
perfection,  because  the  guide  pulleys  have  a  gyratory  motion,  owing  to 
which  their  middle  plane  falls  out  of  its  normal  position,  and  causes  the 
belt  to  be  drawn  off  the  pulley  and  the  angle  of  contact  to  alter.  These 
circumstances  must  lead  to  an  irregularity  in  the  work  of  the  belt-drive. 

However,  the  defects  pointed  out  are  not  very  considerable  and  may 
easily  be  avoided.  For  our  own  part,  we  would  advise  the  constructors 
to  pay  serious  attention  to  the  electromotive  transmission  of  motion  to 
the  sifters,  retaining  the  principle  of  utilising  the  centrifugal  force.  If  a 
friction  clutch  or  a  chain  wheel  were  to  be  set  on  the  shaft  carrying  the 
weight,  as  in  the  case  of  the  American  sifter,  or  on  the  fly-wheel  with  the 
weight,  as  Voll  and  Hertz's  sifter  has  it,  and  bring  it  into  rotation  from 
the  electromotor,1  then  the  complex  ball  drop-hanger  frame,  driving 
belt-pulley,  guide-pulleys,  &c.,  become  quite  superfluous.  To  the  motor 
of  the  sifter  there  will  be  only  wires  running  from  the  ceiling,  which  will 
totally  obviate  the  inconveniences  of  belt-drive,  which  work  here  under 
unfavourable  conditions. 

6.  Capacity  of  Plansifters 

The  capacity  of  sifters,  like  that  of  other  bolting  machines,  is  charac- 
terised not  only  by  the  quantity  of  product  sifted  through  a  unit  of  bolt- 
ing  surface,  but  also  by  the  quality  of  that  work,  i.e.  the  accuracy  in 
separating  the  product  according  to  size.  If  the  overtails  contain  particles 
pf  product,  which,  judging  by  their  size,  should  have  passed  through  the 

i  The  great  number  of  revolutions  of  the  motor  prevents  a  direct  transmission  from  it  to 
the  ny- wheel. 


CHAP,  v]  FLOUR    MILLING  387 

meshes  of  the  sieve,  the  work  of  the  bolting  machine  is  unsatisfactory, 
the  machine  is  overloaded.  When  testing  the  capacity  of  bolting  machines 
we  suppose  the  quality  of  the  work  to  be  defined  with  an  accuracy  of  up 
to  5  per  cent.,  i.e.  the  tails  contain  not  more  than  5  per  cent,  of  the 
product  which  should  have  passed  through  the  sieves. 

The,  capacity  of  plansifters,  as  also  of  reels  and  centrifugals,  is  best 
determined  by  experiment,  but  a  theoretical  elucidation  of  that  question, 
in  the  shape  given  to  it  by  Professor  Zworykin,  deserves  attention. 

First  of  all  it  is  interesting  to  define  the  general  bolting  area  for  a 
given  bulk  of  product,  regarding  the  latter  as  the  capacity  of  the  mill  in 
question. 

We  have  seen  that  the  capacity  of  roller  mills  is  expressed  in  kilo- 
grams thus  : 

Q  =  elvd    ... (1). 

where  I  is  the  length  of  the  rolls,  v  the  velocity  of  passage  of  the  product 
through  the  rolls,  <5  the  distance  between  the  rolls  (average  size  of  the 
product)  or  the  thickness  of  the  sheet  of  product,  and  e  is  the  practical 
alterable  coefficient. 

Professor  Zworykin  takes  the  bolting  capacity  proportionate  to  the 
area  of  the  sieve  and  approximately  proportionate  to  the  square  of  the 
size  of  the  product.     By  this  reason  Q  obtained  from  the  rolls  and  to  be 
bolted  now,  is  expressed  by  the  formula  : 

Q-e^AP      ..   .     .     .     .     .     ...      (2), 

where  A  is  the  bolting  area,  6  largest  size  of  the  product,  and  ex  practical 
alterable  coefficient. 

From  (1)  and  (2)  we  obtain  : 


and  hence  the  A  sought  for  : 

"-,;.;."  '    '    A^J <3>- 

In  this  formula  77  =— . 

The  capacity  Q  of  stone  mills  is  formulated  thus  : 

where  v0  is  the  radial  velocity  of  the  product  discharged,  d  the  average 
dimensions  of  the  product. 
On  the  other  hand 


Consequently, 

A-,  ....     .     ,     .      /:.    (5). 


388 


FLOUR   MILLING 


[CHAP,  v 


If  for  rolls,  both  grooved  and  smooth,  we  accept  the  velocities 
v  to  be  constant,  as  VQ  for  millstones,  the  magnitude  of  the  areas  of 
sieves  will  be  : 


A  -- 


d 


for  roller  mills, 
for  millstones. 


These  formulae  are  useful  only  if  we  have  succceeded  in  deducing 
a  series  of  values  for  tj0  and  r)\  from  practice,  which  requires  serious 
experimental  work  on  a  large  scale.  At  the  present  moment  we  are 
obliged  to  make  use  only  of  the  data  concerning  the  capacity  of  plan- 
sifters  given  by  the  works,  correcting  them  after  the  results  of  practice. 

Comparing  the  capacity  of  different  bolting  machines,  Professor 
Zworykin  gives  the  following  table  (Table  XXXVIII)  : 

TABLE    XXXVIII 


SYSTEM. 

Capacity  of  1  square  metre  bolting 
surface  per  1  hour. 

Polygonal  reel 
Centrifugal      .... 
Haggenmacher's  sifter     . 

up  to  15  klg.  of  flour 
„      70      „ 

„  100     „ 

In  other  terms,  centrifugals  have  a  capacity  4-5  times  greater  than 
reels,  and  the  plansifters  6*5  times. 

According  to  F.  Kick's  researches,  1  square  metre  of  working  surface 
in  Haggenmacher's  sifter  has  a  capacity  only  four  times  as  great  as  that 
of  the  reel. 

Below  we  give  a  table  (XXXIX)  of  the  more  up-to-date  results  as 
regards  the  capacity  of  reels,  centrifugals  and  sifters  according  to  Baum- 
gartner  and  Notovitch. 

TABLE   XXXIX 


Product  to  be  Sifted. 

Area  of  Sieves  in  Square  Metres  for  Boiling  36  Ib.  of  Product 
per  1  Hour. 

Polygonal  Reels. 

Round  Reels. 

Centrifugals. 

Plansifter. 

1  .  Break  Chop   . 
2.  Fine  Chop  (midds  etc.) 
3.  Reduction  50-60  per'l 
cent,  of  flour  and  50-40  1 
per  cent,  of  dunst  .      .  J 

0'123sq.m. 
0-350     „ 

0-50       „ 

0-110  sq.m. 
0-140     „ 

0-160     „ 

0-025sq.m. 
0-070     „ 

0-100     „ 

0-230  sq.m. 

0-330     „ 

' 

CHAP.    V] 


FLOUR   MILLING 


389 


When  calculating  the  number  of  sifters  required  for  the  given  capacity 
of  the  mill,  Table  XL  may  be  used,  where  the  capacity  of  two-box 
sifters  with  two,  three  and  four  sections  having  different  numbers  of 
bolting  trays  is  given. 


TABLE    XL 


1 

Number  of 

Dimensions  of             Capacity  of  the  Sifter 
Bolting  Trays.              in  Cwts.  per  1  Hour. 

1 

.5 
*>§ 

Wheat. 

Rye. 

What  Part  of  the 

§ 

e 
a 

g 

8 

Sifter. 

& 

"2    j 

. 

1 

S3  JS 

§ 

| 

6 

Si8 

|1L| 

•sH 

1 

2  c8 

a 

n 

88 

eq 

o 

8 

2 

53-0 

27-3 

33-6 

Whole  sifter 

3 

10     !   1400 

865 

26-2 

13-6 

16-8 

\  of  sifter 

4 

... 

... 

13-0 

6-5 

7-8 

4                           55 

2 

63-5 

31-2 

40-0 

\  of  sifter 

3 

12 

1400 

865 

31-0 

15-6 

20-0 

43 

SJ                            55 

4 

14-7 

7-2 

9-5 

1 

i 

cS 

$ 

2 

... 

... 

... 

50-0 

22-0 

27-3 

N 

^  of  sifter 

3 

6 

1600 

925 

25-0 

11-0 

13-6 

£ 

\ 

4 

... 

... 

... 

12-0 

4-8 

6-1 

O 
ft 

i 

2 

55-8 

27-3 

33-6 

O 
IQ 

^  of  sifter 

3 

8        1600 

925 

27-9 

13-6 

16-8 

O 

i 

4 



13-4 

6-1 

7-8 

5 

i 

! 

CO 

0 

' 

2 

.  .  . 

... 

67-4 

33-6 

41-5 

a 

^  of  sifter 

3 

10 

1600 

925 

33-7 

16-8 

20-8 

s 

t 

4 

16-3 

7-8 

9-8 

4                          55 

2 

79-0     40-0 

49-2 

i  of  sifter 

3 

12 

1600 

925 

39-5 

20-0 

24-6 

2"                 ?  j 

4 

... 

... 

... 

19-0 

9-5 

11-9 

1 

The  capacity  of  round  sifters  of  the  Bunge  type  is  given  in  Table 
XLI. 


390 


FLOUR   MILLING 
TABLE    XLI 


[CHAP,  v 


i 

(Capacity  of  Sifter  in 

rp                   Bolting  Trftys 
in  mm. 

Working 
Surface  in 

Mt.2 

Number  of 
Revolutions 
per  Minute. 

Cwts.  per  Hour. 

Power 
Consumption, 
H.P. 

Break  Chop. 

Reduction 
Stock. 

11000              3-1 

( 

12-2 

7-4 

0-12 

1300 

5-2 

\        H0        J 

21-0 

12-2 

0-15 

1500 

7-0 

I                        1 

28-5 

16-2 

0-20 

1700 

9-0 

J                        ' 

36-5 

20-3 

0-25 

(        1000 
5                 1300 

4-0 
6-6 

( 

14-8 
24-3 

9-0 
14-8 

0-15 
0-20 

trays  1        1500 

8-8 

-      150     \ 

32-4 

18-7 

0-25 

1700 

11-3 

40-5 

1 

24-3 

0-30 

In  spite  of  this  table  showing  the  capacity  of  round  sifters  to  be 
almost  the  same  as  that  of  rectangular  ones,  in  reality  it  should  be  re- 
garded as  much  smaller  (up  to  25  per  cent.),  taking  into  consideration 
the  quality  of  work,  which  is  incomparably  lower  than  the  work  of 
rectangular  sifters,  where  it  is  performed  on  six  trays  at  least. 

In  comparing  the  quantity  of  work  done  by  plaiisifters  and  the  other 
bolting  machines,  we  see  that  the  sifter  stands  considerably  higher  as 
regards  capacity.  But  the  quality  of  work  of  the  sifter  is  also  higher 
than  that  of  polygonal  and  round  reels.  Experiments  prove  that  at 
the  bolting  of  the  products  (reduction  of  middlings)  some  50  per  cent,  of 
flour  is  tailed  over,  together  with  fine  middlings  and  dunst,  which  makes  a 
complementary  bolting  indispensable,  in  its  turn  requiring  a  considerable 
increase  of  the  working  surface  of  the  sieves. 

Since  there  are  no  investigations  of  the  quality  of  work  performed  by 
sifters  and  reels  of  a  later  date,  we  shall  give  the  results  of  experiments 
made  by  I.  Wingert,  the  president  of  the  German  Millers'  Society, 
who  tested  Haggenmacher's  sifter  and  the  reel,  and  published  the 
results  of  his  investigations  in  Die  Muhle,  1889,  No.  6.  The  experi- 
ments were  performed  on  the  bolting  of  the  product  of  middlings  reduced 
on  French  stones.  The  results  were  as  follows  : 


Flour  . 
Middlings 
Offal 


Sifter. 

Reel. 

74-52  per  cent. 

43-83  per  cent 

25-36        „ 

54-46        „ 

0-12 

1-71        „ 

100  per  cent.  100  per  cent. 


CHAP,  v]  FLOUR   MILLING 

Thus,  more  than  a  half  of  the  flour  and  dunst,  which  could  have  been 
discharged  with  the  flour,  were  separated  as  middlings  on  the  reel 
(54-46  per  cent.),  whereas  the  sifter  yielded  25-36  per  cent,  of  pure  middlings 
unmixed  with  flour. 

The  advantage  of  plansifters  in  comparison  to  other  types  of  bolting 
machines  needs  no  proofs  now.  And  if  the  reels  are  not  generally 
supplanted  as  yet,  they  are  retained  only  in  primitive  mills,  where  the 
quality  of  the  flour  is  of  no  importance,  or  this  flour  has  to  compete  with 
flour  of  unsifted  grinding,  as  in  peasant  windmills,  or  water-mills  of  the 
Caucasian  type. 


CHAPTER    VI 

GRADING   THE    PRODUCT   ACCORDING   TO    SPECIFIC 

GRAVITY 


GRADING  MIDDLINGS  AND  DUNST  ACCORDING  TO  SPECIFIC  GRAVITY 

SINCE  the  flour -milling  technics  evolved  the  system  of  high  grinding,  the 
sorting  of  the  intermediate  product  according  to  its  specific  gravity  has 
been  undoubtedly  one  of  the  most  important  stages  in  the  milling  process. 
Indeed,  from  the  moment  he  has  separated  the  middlings  and  the  dunst 
according  to  the  quality,  the  miller  proceeds  to  define  the  grades  of  flour. 
The  removal  of  the  branny  and  colouring  particles  of  grain  from  the 
valuable  starchy  middlings,  which  give  high  grades  of  flour,  is  no  easy  task. 
A  solution  of  this  problem  was  being  sought  by  flour-milling  engineers 
for  a  whole  century,  and  only  now  is  it  solved  almost  to  perfection. 

Although  the  repeated  milling  (mouture  bconomique)  is  an  invention 
of  the  French,  who  practised  it  150  years  ago,  the  character  of  the 
wheat — soft,  with  comparatively  moist  integument — never  suggested 
to  the  French  flour-millers  the  idea  of  grading  the  middlings  according 
to  quality.  In  the  old  French  process  of  repeated  milling1  the  elastic 
coverings  of  the  soft  wheat  very  successfully  resisted  reduction  when 
passed  through  grinding  machines,  and  gave  a  comparatively  insigni- 
ficant percentage  of  bran  reduced  to  flour.  A  considerable  part  of  the 
integument  therefore  was  easily  removed  with  the  aid  of  bolting  apparatus. 
The  result  of  a  repeated  milling  of  hard  wheats  is  totally  different.  The 
dry  shells  are  reduced  to  fine  bran,  which  it  is  impossible  to  separate  from 
the  meal  by  bolting  machines.  The  fine  bran  imparts  a  darker  colouring 
to  the  flour  and  lowers  its  quality  and  market  value. 

The  French  repeated  milling,  widely  spread  in  Europe,  with  the  aid 
of  which  an  excellent  flour  according  to  the  standard  of  the  time  was 
obtained,  proved  to  be  unsuited  for  hard  Hungarian  wheats.  With 
a  view  to  attaining  the  same  results  in  milling  as  with  the  soft  wheats 

1  As  a  type  of  such  milling,  the  rye  milling  of  to-day  may  be  taken,  with  the  sole  difference 
that  roller  mills  are  substituted  in  the  place  of  grindstones. 


CHAP,  vi]  FLOUR   MILLING  393 

the  Hungarian  flour-millers  thought  of  damping  the  wheat,  so  as  to 
moisten  the  bran,  and  in  this  manner  make  it  more  elastic.  The  imperfect 
damping  processes,  however,  offered  great  inconveniences,  in  so  far  that 
the  wheat  was  moistened  too  copiously,  the  moisture  penetrated  into  the 
kernel  of  the  wheat,  the  flour  obtained  was  "  damp,"  and  could  not  stand 
long  storage  or  export. 

Thus  the  first  impetus  was  given  to  the  Hungarian  millers  to  direct 
their  inventive  faculty  towards  other  ways  of  freeing  the  flour  of  branny 
admixtures.  In  the  first  place,  Ignatz  Paur,  a  flour  miller,  introduced  a 
slight  improvement  into  the  French  repeated  milling,  by  greatly  altering 
the  distances  between  the  working  surfaces  of  the  grinding  stones,  and 
thus  making  the  first  steps  towards  modern  high-milling  (Hochmiihlerei 
is  derived  from  Hochmiihle,  showing  that  the  runner  stands  high  over 
the  bed-stone  in  the  first  passage),  and  then,  winnowing  the  blue  flour 
away  from  the  heavy  semolina  by  means  of  hand  bellows,  the  primitive 
shape  of  a  special  type  of  purifiers,  which,  however,  took  no  root  in 
practice. 

Owing  to  this  improvement  Austria-Hungary  first  sent  to  the  market 
a  granular  flour  for  bread  of  the  highest  grade  and  semolina  for  immediate 
use.  That  semolina,  very  much  resembling  our  "  manna,"  was  called 
Wiener  Gries,  i.e.  Viennese  semolina. 

Thus,  the  hand  bellows  gave  Ignatz  Paur  the  idea  of  sorting  the  pro- 
duct according  to  quality,  i.e.  specific  gravity.  In  1810  he  invented  the 
first  purifier  which  is  known  in  the  history  of  the  development  of  flour 
milling  under  the  name  of  "  The  Viennese  purifier."  From  that  date 
the  milling  process  is  richer  by  a  very  important  stage — grading  of 
middlings  according  to  the  quality. 

For  the  period  of  a  century  flour  milling  has  seen  hundreds  of  con- 
structions of  purifiers,  but  the  fundamental  principle  of  their  action  has 
remained  the  same.  For  this  reason,  before  proceeding  to  review  the 
purifiers  in  their  historic  succession,  beginning  with  Ignatz  Paur's,  it  is 
necessary  to  dwell  on  the  theoretic  foundation  of  the  chief  principle  of 
action  of  every  purifier. 

If  we  compare  the  weights  of  equal  bulks  of  cleaned  and  uncleaned 
middlings,  both  kinds  being  of  equal  size,  we  shall  see  that  the  impure 
middlings  are  less  in  weight.  This  weight  is  lost  at  the  expense  of  the 
grains  of  middlings,  which  have  one  of  their  facets  covered  with  the 
integument  of  the  kernel,  because  the  bran  in  specific  gravity  is  much 
lighter  than  the  inner  starchy  parts  of  the  wheat  or  rye.  Further, 
the  weight  of  uncleaned  middlings  is  less  owing  to  the  splinter-like 


304 


FLOUR   MILLING 


[CHAP,  vi 


particles  of  the  bran,  which  pass  as  throughs  or  overtails  from  one  and 
the  same  sieve  together  with  the  good  middlings.  In  this  manner  after 
sifting  we  have  a  mixture  of  particles  equal  in  size  but  unequal  in 
weight.  It  was  that  difference  in  the  weight  of  separate  particles  that  the 
constructors  availed  themselves  of,  to  separate  the  light  particles,  i.e. 
bran  and  middlings  with  integumental  elements,  from  the  heavy  or,  in 
other  terms,  rich  product. 

It  is  evident  that  if  two  falling  grains  of  product,  equal  in  size  but 
different  in  weight,  should  be  subjected  to  the  action  of  an  air-current, 
the  lighter  particle  of  grain  will  be  carried  further  than  the  heavier  one. 
But  for  the  constructor  of  a  machine  sorting  the  middlings  according 


\ 


V        \ 

FIG.  379. 

//—Direction  of  the  wind. 

to  quality,  it  is  important  to  know  not  only  this  obvious  fact,  but  also 
the  law  of  motion  of  the  particles  influenced  by  their  gravity  and  the 
constant  force  of  wind  fanning  the  product  to  be  graded.  And  only 
when  that  law  of  motion  has  been  defined,  is  the  constructor  enabled  to 
start  working  out  a  rational  type  of  machine  confidently,  and  without 
groping  about  for  a  rational  type  of  machine. 

Thus,  we  are  to  solve  the  following  problem  :  to  define  the  law  of 
motion  of  a  particle  subjected  to  the  action  of  two  constant  forces. 

We  shall  first  examine  a  general  case,  when  the  particle  faUs  into  the 
sphere  of  action  of  the  draught  with  a  certain  initial  velocity  v0.  For 
simplicity's  sake  let  us  imagine  (Fig.  379)  we  have  an  inclined  spout  T, 
down  which  the  product  flows  into  the  chamber  Q  with  that  same  initial 
velocity  v0.  On  leaving  the  spout  the  particles  of  middlings  undergo 
fanning  by  a  horizontal  air-current. 


CHAP,  vi]  FLOUR   MILLING  395 

We  suppose  0,  where  a  particle  of  the  stock  m  is  on  passing  from  the 
spout  in  Q,  to  be  the  beginning  of  rectangular  co-ordinates,  of  which  OX 
coincides  with  the  direction  of  the  draught,  and  0  Y  with  the  vertical,  i.e. 
with  the  direction  of  action  of  the  gravity.  The  velocities  a  and  6  are 
components  of  the  initial  velocity  v0. 

On  marking  the  force  of  the  draught  mw,  where  w  is  the  acceleration  of 
motion  along  OX,  we  obtain  the  following  equations  of  motion  for  the 
particle  of  stock  m  : 


mw= 


—mw 


dt* 
or 


w^ &• 


To  define  the  laws  of  motion  along  OX  and  OY,  we  must  evidently 

egrat' 
obtain  : 


dx 

integrate   these   equations.     Then,    bearing   in   mind    that  -r-=Vx,   we 


|3F 


To  define  the  constant  C  we  suppose  t=o,  i.e.  we  define  Vx  at  the 
initial  moment  of  motion.  Then,  naturally  C——a  from  Vx-\-C=O. 
Consequently,  the  law  of  velocity  is  : 


,    ,    .    .     .    .     .    .   (3). 

By  integrating  a  second  time,  we  obtain  : 

\dx  =  \adt+  \wtdi 


or 


But  since  t=o,  we  have  x=o,  consequently  0-^=0.     Thus  the  law  of 
motion  along  OX  is  : 

.     .     ......     (I). 


Having  done  the  same  with  the  differential  equation  of  motion  (2) 
along  the  axis  OF  we  obtain  : 

.  '.    .    .'.    .    .    •    (II). 


Now,  to  define  the  trajectory  of  motion  of  the  particles,  we  must 
exclude  t  out  of  (I)  and  (II).     By  reducing  these  equations  to  the  same 


396  FLOUR   MILLING  [CHAP,  vi 

denominator,  multiplying  I  by  g,  II  by  w,  and  subtracting  the   second 
from  the  first,  we  obtain  : 

2x=2at+wt2    I    g 

2y=2bt+gt2     \     w 

2(gx—wy)=2(ag—bw)t 

Hence  we  define  t=^X~^  and  substitute  it  into  the  second  equation. 
ag  —  bw 

Then  we  "have  : 

2 


After  reducing  x  and  y  to  the  same  denominator  and  arranging  them 
according  to  degrees,  we  obtain  the  equation  of  the  curve  : 

gsx  —  2g2wxy  -\-gwzy2  +2bg(ag  —  bw)x  —  2ag(ag  —  bw)y  =0. 

Consequently,  we  obtain  a  curve  of  the  second  order  of  the  follow- 

ing shape  : 

Axz+Bxy+Cy*+Dx+Ey=Q. 

The  absence  of  the  constant  term  F  shows  that  the  curve  passes 
through  the  beginning  of  the  co-ordinates,  as  it  should.  The  term 
B2  —  4AC,  after  the  substitution  of  corresponding  coefficients  (A=g*, 
B=—2gw2,  and  C=gw2),  is  equal  to  0.  Hence  it  follows  that  our  curve 
is  a  parabola,  one  branch  of  which  passes  through  the  point  0. 

Now  the  position  of  the  axis  of  the  parabola  remains  to  be  defined. 
For  the  equation  of  the  axis  of  the  parabola  in  general  outlines  we  have  the 
following  formula  :  l 


Having  substituted  the  corresponding  coefficients  A,  B,  C,  D,  and  E 
we  obtain  the  following  equation  of  the  axis  : 

-g(w2+g2)x+w(w2+g*)y-(ag-bw)(bg+aw)=0, 
or 

l     '     '     '     ^      '' 


In  this  way  the  axis  of  the  parabola  lies  crossing  the  axis  7  below  the 
point  0  and  the  axis  X  to  the  left  from  the  beginning  of  the  co-ordinates, 
because  we  see  from  the  equation  of  the  parabola  axis  that  the  segment 
it  strikes  off  the  axis  X  has  a  negative  magnitude.  The  direction  of  the 
parabola  axis  will  be  defined  in  accordance  with  the  angular  coefficient, 

1    Analytical  Geometry,  Briot  and  Bonquet,  p.  148. 


CHAP,  vi]  FLOUR    MILLING  397 

which  will  give  us  a  very  simple  formula  for  the  equation  of  the  axis  we 
have  obtained  : 


If  we  define  now  the  direction  of  the  resultant  of  two  component 
forces  mw  and  mg  we  obtain  from  the  triangle  OES  : 

mg—mwtgy,  whence  tg<p=—. 

Consequently,  the  axis  of  the  parabola  is  parallel  to  the  direction  of 
the  resultant  force.  The  summit  of  the  parabola  is,  evidently,  higher 
than  the  axis  of  X  is,  for  instance,  at  the  point  N.  It  is  possible  to 
find  the  summit  of  the  parabola  and  the  equation  (III)  of  its  axis. 

We  have  thus  solved  the  problem  in  its  general  form.     The  formula 

tg<p=—  defines  the  direction  of  the  axis  of  the  parabola,  which  is  very  easy 

to  construct.  Since  w,  the  acceleration  of  the  particle  through  the  force 
of  the  draught,  depends  on  the  shape  of  the  particle,  and  the  force  of  the 
draught  expressed  by  the  product  of  the  mass  by  the  acceleration  mw,  it  is 
clear  that  for  particles  of  different  quality  and  shape  we  shall  have  different 
directions  of  motion,  i.e.  shapes  of  parabolas  ;  the  trajectories  of  motion 
will  be  different  for  particles  of  unequal  quality  and  form  of  their  surface. 
It  follows  hence  that  we  can  set  the  receiving  hoppers  for  particles  of 
various  quality  accurately  and  correctly,  once  the  trajectories  of  motion 
are  designed. 

Besides  that  general  problem,  special  cases  are  possible.  Firstly,  the 
particles  having  an  initial  velocity,  developing,  for  instance,  from  the 
centrifugal  motion,  are  exposed  to  the  effect  of  the  draught  at  an  angle  of 
0°  to  the  direction  of  the  gravity  ;  secondly,  the  force  of  the  draught  is 
directed  at  an  angle  of  180°  to  the  gravity.  Both  in  the  first  and  in  the 
second  cases  we  have  the  simplest  problem  in  parabolic  motion.  The 
summit  of  the  parabola  coincides  in  both  these  cases  with  the  beginning 
of  the  co-ordinates. 

Let  us  turn  now  to  the  first  purifier,  invented  by  Ignatz  Paur  as  early 
as  in  1807,  and  patented  in  1810. 

In  its  original  form  this  purifier  (Fig.  380)  was  a  timber  box  of  a 
parallelepiped  shape  9x2jxlJ  ft.  in  size.  Generally  the  chamber  of 
the  purifier  was  divided  into  three  nearly  equal  parts,  D,  E,  and  F,  work- 
ing independently  of  each  other.  As  may  be  seen  in  the  longitudinal 
section  (Fig.  P)  of  the  purifier,  its  box  is  divided  into  three  chambers  by 
air-conducting  channels  C  and  B  directing  the  air  to  the  product  to  be 


398 


FLOUR   MILLING 


[CHAP,  vi 

graded.  Each  chamber 
of  the  purifier  was  sup- 
plied by  the  spouts  a,  a', 
and  a",  through  hoppers 
I,  b',  and  b"  with  product 
which  was  previously 
graded  on  a  flat  sieve, 
likewise  of  Paur's  con- 
struction. The  operation 
in  all  the  chambers  being 
perfectly  alike,  it  is 
sufficient  to  examine  one 
section,  D. 

The  product  in  pass- 
ing through  the  outlet  of 
the  hopper  b  into  the 
hopper  /  was  subjected 
to  the  effect  of  an  air- 
current  blowing  through 
the  opening  a  out  of  the 
air-conductor  C.  The 
branny  and  light  mealy 
particles  were  carried 
away  to  section  V9  the 
heavier  ones  fell  into  the 
hopper  //,  and  in  this 
way,  on  the  top  floor  of 
the  purifier,  the  first  separ- 
ation of  the  product  into 
three  classes  according  to 
the  quality  was  effected. 

When  running  from 
hopper  /  to  ///  and 
from  hopper  II  to  IV  the 
stock  underwent  fanning 
for  the  second  time  by 
a  draught  impelled 
through  the  opening  av 
The  product  was  con- 
sequently subjected  to  a 


CHAP.    VI] 


FLOUR   MILLING 


399 


double  aspiration,  and  then  delivered  through  outlets  g  and  h  into 
sacks.  Thus,  three  products  were  obtained  on  Paur's  purifier  ;  two 
grades  of  middlings  of  different  quality  and  light  refuse. 

To  have  done  with  that  purifier  we  must  complete  the  description  of 
its  construction.  As  we  see  in  Fig.  P,  the  hoppers  /,  II,  III,  IV,  and  V 
are  separated  by  swinging  partitions  *,  by  means  of  which  the  area  of 
cross-section  of  the  air- current  could  be  altered,  and  thus  the  velocity 
of  the  passage  of  air  regulated,  which  allowed  of  adapting  the  purifier 
to  treat  products  of  different  size  and  quality.  Fig.  Q  illustrates  the  cross 
section  of  the  purifier  where  the  hoppers  /  and  ///  and  the  screws  o  to  the 
gate  m  (Fig.  R)  are  seen,  which  regulates  the  influx  of  air  from  the  air- 


FIG.  381. 

conductors  C  and  B.  On  Fig.  S  is  given  a  rather  primitively  constructed 
fan  which  was  generally  set  somewhere  apart  in  a  convenient  place,  and 
communicated  with  the  purifier  through  the  main  air-conductor  A. 
This  air-conductor  with  two  channels,  C  and  B,  branching  off,  one  of 
which,  B,  works  for  two  chambers  E  and  F,  protrudes  beyond  C  to  showT 
that  it  supplies  with  air  other  purifiers  as  well.  The  Fig.  R  gives  an  idea 
of  the  nozzle  conducting  the  air  into  hoppers  /  and  77.  In  this  draw- 
ing the  gate  m  regulating  the  influx  of  air  by  means  of  the  screw  o  is 
clearly  seen. 

A  few  years  later  Paur  brought  out  a  more  perfect  construction  of  a  puri- 
fier (Fig.  381),  which  constituted  one  block  with  the  fan  v  and  was  combined 
with  a  vibrating  sieve  b  and  an  automatic  elevator  E.  We  shall  say  no 
more  of  this  purifier,  because  it  is  clearly  enough  described  in  the  preceding, 


400 


FLOUR   MILLING 


[CHAP,  vi 


Paur's  purifier  and  other  machines  of  the  same  type,  and  built  on  the 
same  principle,  were  in  use  in  mills  for  sixty  years.  Having  spread 
all  over  Europe,  they  were  called  "  Wiener  Griesputzmaschinen  mit 
Stosswind,"  or  simply  "  Wiener  Stossmaschinen."  This  "  Stosswind," 
i.e.  the  air  forced  into  the  machine,  caused  the  flour  millers  no  small 
annoyance,  as  the  mill  was  filled  with  clouds  of  flour  dust,  which  freely 
escaped  from  the  purifier  driven  by  the  impelled  air.  Naturally,  there 
was  a  series  of  attempts  to  obviate  this  inconvenience,  but  they  all  were 
constructive  half -measures  which  brought  no  satisfactory  results. 

But,  in  1867,  J.  Woerner's  purifier  made  its  appearance,  and  im- 
mediately drove  out  the  machine  with  the  Stosswind  that  blinded  the 
mill  with  flour-dust.  The  new  machine  differs  from  the  machines  of  the 


FIG.  382. 

Paur  type  in  that,  instead  of  a  blast  fan  Woerner  adopted  an  exhaust 
one.  In  this  way  the  fan  not  only  does  not  fill  the  mill  with  dust,  but 
on  the  contrary  cleans  it. 

Woerner's  purifier  (Fig.  382)  was  a  box  of  about  the  same  size  as  Paur's 
machine,  also  divided  into  three  chambers  A,  B,  and  C.  Over  the  puri- 
fier there  was  the  sieve  b  to  which  a  vibratory  motion  was  imparted  with 
the  aid  of  a  crank  shaft  v  receiving  its  motion  from  the  ceiling  drive 
through  the  belt-pulley  d.  On  the  same  shaft  v  was  a  hand-wheel  ra 
adjusting  the  reciprocating  movement  of  the  sieve,  which  was  swinging 
on  rods  n.  The  air  conductors  kk  communicate  with  the  general  air- 
channel  running  to  the  aspirating  fan. 

The  product,  graded  according  to  size  into  three  grades,  flows  into 
separate  chambers  of  the  purifier  through  hoppers  c,  c',  and  c".  The 
process  of  grading  according  to  the  quality  in  the  chamber  A  is  carried 


CHAP.    VI] 


FLOUR   MILLING 


401 


out  in  the  same  order  as  in  B  and  C.  From  the  hopper  c  the  semolina 
falls  into  divisions  /,  /',  and  I",  undergoing  a  triple  fanning  by  a  draught 
aspirated  through  the  opening  g.  The  lightest  particles  of  bran  and  dust 
pass  into  division  ///,  and  are  carried  out  through  the  air  trunk  kk  driven 
by  the  fan  into  the  dust  chamber  ;  the  second  grade  of  middlings  falls 
into  division  //  and  is  subjected  to  a  twofold  fanning.  By  this  method 
here,  too,  as  in  Paur's  purifier,  three  products  are  obtained,  with  the  sole 
difference,  that  the  light  refuse  of  Paur's  purifier  covered  the  mill  with  dust, 
while  here  they  could  collect  in  the  dust  chamber,  or  at  least  be  discharged 
into  the  open.  As  we  see  in  the  drawing,  in  the  purifier  the  velocity  and 
the  quantity  of  air  employed  could  be  regulated  by  means  of  the  swinging 
gates  i.  The  purifier  was  covered  on  the  sides  by  a  timber  casing  in  which 
windows  /  were  made  for  inspecting  the  operation. 

On  this  new  principle  of  the  "  Saugwind,"  i.e.  on  the  principle  of 
operating  by  means  of  a  current  of  as- 
pirated air,  there  sprung  up  a  series  of 
more  or  less  successful  types  of  purifiers, 
still  working  with  a  flat  vibrating  sieve 
outside  the  purifier  itself. 

Of  these  purifiers,  of  a  slightly  simplified 
type  worked  in  comparatively  simple  mills, 
we  should  mention  Arndt's  machine, 
which  made  its  appearance  in  1869. 
As  may  be  seen  in  the  drawing  (Fig.  383),  the  middlings  fell  through 
the  hopper  T  upon  the  sieve  C  which  was  given  a  vibratory  recipro- 
cating motion  (up  to  200  vibrations)  by  a  crank  mechanism  b-i. 
The  end  of  the  sieve  was  laid  on  rolls  g.  There  were  only  two  products 
here  :  the  throughs  which  ran  into  the  feeding  hopper  Q  and  spout  a, 
and  the  refuse  which  was  discharged.  The  fanning  of  the  product  was 
performed  by  draughts  impelled  through  tubes  a,  d,  and  c ;  the  air  was 
sucked  in  by  fans  F-  V  ending  in  tubes  /  with  bags  tied  to  them  for  col- 
lecting the  flour  dust  and  the  light  branny  refuse.  The  highest  quality 
middlings  passed  into  c  and  those  of  a  second  quality  into  the  side  spouts 
d.  At  the  ends  of  spouts  c  and  d  there  were  set  bosses  p  and  q,  having  side 
openings  for  letting  the  air  out ;  to  these  bosses,  which  could  be  lowered 
and  raised  to  regulate  the  inflow  of  air,  there  were  bags  attached  to  receive 
the  cleaned  middlings.  The  tubes  /  were  furnished  with  windows  e 
covered  with  a  bolting  or  linen  frame  to  leave  a  passage  for  the  air  and 
prevent  the  meal  dust  and  particles  of  bran  from  escaping. 

For  a   period   of  ten  years  after  Woerner's  purifier  was  invented, 

2c 


FIG.  383. 


402  FLOUR   MILLING  [CHAP,  vi 

this  type  of  machine  was  being  perfected,  mainly  in  the  direction  of 
a  multiple  aspiration  and  the  increase  of  the  number  of  grades  of 
middlings. 

The  most  successful  and  characteristic  machines  in  that  respect  are 
the  purifiers  of  Millot  and  of  Karl  Haggenmacher,  which  appeared  almost 
simultaneously  (the  first  in  1879,  the  second  in  1878). 

Millot 's  purifier,  shown  in  a  longitudinal  and  in  a  transversal  section 
in  Figs.  384  and  385,  was  designed  to  give  a  multiple  fanning  to  the  pro- 
duct which  poured  into  the  hoppers  through  the  sieves  TT'  (Fig.  384)  and 
passed  through  the  funnel  m  to  be  graded.  The  sieve  with  the  hoppers 
was  fixed  on  four  elastic  stands  t  and  vibrated  from  the  eccentric  rods  s 
operating  from  the  shaft  o,  which  carried  the  intermediate  belt-pulley  0 
to  the  fan  pulley  0'.  The  stock  was  conveyed  (Fig.  384,  right-hand  side) 
by  the  channel  d  to  the  first  sieve  c  through  which  the  air-current  passed. 
The  refuse  off  the  sieve  c  flowed  down  an  inner  channel  to  be  further  aspir- 
ated, while  the  throughs  fell  on  an  inclined  receiving  board,  down  which 
it  rolled  on  to  the  other  sieve  c  similar  to  the  one  preceding.  This  reiter- 
ated process  of  fanning  one  and  the  same  product  was  continued  until 
the  cleaned  middlings  reached  the  receiving  spout  d'  and  were  discharged 
into  the  sack.  The  particles  of  bran  and  the  meal  dust,  on  passing  the 
grates  E,  were  blown  by  the  fan  V  into  the  dust  chamber,  whereas  the 
heavier  particles,  dropping  to  the  bottom,  left  the  purifier  through  the 
chamber  D' '.  In  this  manner  only  two  grades  of  middlings  were  yielded 
by  this  purifier,  but  these  were  well  cleaned. 

For  regulating  the  force  of  the  draught  there  were  apertures  F,  the 
opening  of  which  allowed  a  passage  for  the  air  and  reduced  the  rarefac- 
tion in  the  chambers  D.  Besides  that,  there  were  automatic  valves  F', 
which  opened  by  themselves  as  soon  as  the  rarefaction  in  the  chambers  D 
exceeded  the  set  limits.  On  Fig.  385  is  shown  the  chamber  G  into  which 
there  passes  a  part  of  the  fanned  air,  cleaned  by  filtering  through  linen 
tissue  g.  Through  this  chamber  G  the  air  was  directed  by  gutta-percha 
sleeves  r  under  the  sieves  T  and  T'  and  cleaned  their  blinded  meshes  by 
pressure. 

From  this  description  we  may  judge  how  thoughtfully  this  machine 
was  constructed.  In  the  construction  of  Millot's  machine  all  the  funda- 
mental principles  of  a  purifier  were  foreseen  :  manifold  aspiration,  regula- 
tion of  the  air  pressure,  and  cleaning  of  the  sieve.  Still  Haggenmacher's 
purifier  was  a  more  perfect  type  of  the  machine,  in  so  far  that  it  afforded 
the  possibility  of  obtaining  three  grades  of  middlings.  Altogether, 
it  must  be  noted  that  K.  Haggenmacher  is  one  of  the  most  eminent 


CHAP.    VI] 


FLOUR   MILLING 


403 


404 


FLOUR    MILLING 


[CHAP,  vi 


constructors  of  mill  machinery,  justly  occupying  a  place  of  honour  in  the 
history  of  the  development  of  flour  milling.  We  shall,  therefore,  meet 
his  name  more  than  once  again,  when  studying  the  constructions  of 
machines. 

Haggenmacher's  purifier  is  shown  in  Fig.  386.  Here  we  see  the  same 
scheme  of  vibrating  sieves  a  and  a',  delivering  their  throughs  to  the  hoppers 
d  (two  on  the  right  and  two  on  the  left-hand  side  of  the  purifier),  and  the 
refuse  into  the  hoppers  ~b'  and  b .  The  middlings  of  the  highest  quality  after 
a  quadruple  exhaust  pass  to  the  spout  p,  those  of  medium  to  q,  and 
finally,  the  lower  grade  to  r.  The  meal  dust  and  particles  of  bran  on  pass- 


FIG.  386. 

ing  through  the  fan  V  are  conveyed  by  the  air-trunk  B  to  the  dust 
chamber.  The  outer  air  flows  in  through  the  openings  s1  and  s2,  which 
are  furnished  with  lids  on  hinges  ;  these  lids  may  be  raised  by  the  pres- 
sure of  the  outside  air,  thus  closing  the  openings,  and  drop  under  their 
proper  weight.  But  the  rarefaction  of  air  in  the  chamber  of  the  purifier 
may  be  also  effected  by  the  windows  1,  2,  3,  and  4,  through  which  the 
desired  quantity  of  outer  air  is  let  in,  as  these  windows  may  be  opened 
more  or  less  by  rack  gates  m. 

In  the  beginning  of  the  eighties  the  construction  of  this  purifier  was 
altered,  so  that  it  could  yield  up  to  five  grades  of  middlings.  A  general 
installation  of  these  purifiers  is  seen  in  Fig.  387.  The  sieves  db  here  are 
placed  outside  the  machine,  and  the  stock,  graded  according  to  size  on  the 
sieve,  is  delivered  to  the  purifier  by  an  automatic  elevator  E.  The  fans 


CHAP.   VI] 


FLOUR   MILLING 


405 


are  likewise  set  outside  the  purifier  and  communicate  with  them  by  means 
of  aspirating  air  conductors  o  (collector)  and  o'  (branches  off  to  the  puri- 
fiers). The  graded  product  runs  to  the  ground  floor  to  be  packed. 

The  further  improvement  of  Haggenmacher's  purifier  stands  in  con- 
nection with  the  invention  of  plansifters.  But  substantially  the  last 
types  of  these  machines  remained  purifiers  with  many  aspirations,  in 
which  the  sieves  form  a  separate  independent  machine.  We  shall  return 
again  to  the  latest  types  of  these  purifiers,  and  turn  our  attention  for 
the  present  to  a  new  group  of  machines  for  grading  middlings. 

The  fundamental  principle  of  action  in  the  machines  of  the  first 
group  was  the  aspiration  of  stock  falling  because  of  the  force  of  gravity. 


FIG.  387. 

In  the  seventies,  however,  there  appear  machines  in  which,  besides  the 
force  of  air  currents  and  gravity,  an  attempt  was  made  to  introduce 
centrifugal  force. 

In  1876  such  a  machine  (one  of  the  first)  was  patented  by  Buchholtz. 
The  action  of  this  machine  (Fig.  388)  was  as  follows.  The  stock 
flowing  through  the  hopper  a,  upon  the  rapMly  rotating  disc  c  is  spread 
out  through  the  effect  of  centrifugal  force  and  fanned.  The  heaviest 
particles  fall  into  the  chamber  n,  the  medium  ones  into  m,  and  the  bran 
and  meal  dust  into  the  air-trunk  d,  which  communicates  with  the 
suction  fan.  The  boss  b  with  a  hand-wheel  may  be  raised  or  lowered 
(screw  thread),  which  allows  of  regulating  the  flow.  From  n  and  m  the 
product  is  removed  by  scrapers,  or  runs  down  the  inclined  hopper  to  the 
spout. 


406 


FLOUR   MILLING 


[CHAP,  vi 


Another  machine,  constructed  by  two  Englishmen,  F.  Thomson  and 
W.  Williamson,  in  1880,  is  based  on  the  same  principle,  but  a  repeated 
aspiration  of  the  stock  is  introduced  by  this  time.  Through  a  funnel  z 
(Fig.  389)  the  stock  is  poured  upon  the  rapidly  rotating  disc  t,  from  which 
it  is  flung  off  by  the  action  of  the  centrifugal  force  and  subjected  to 
aspiration.  Successively,  according  to  its  quality,  the  stock  falls  into 
&s,  &2>  &i>  while  the  offal  is  carried  away  through  the  tube  r  to  the  dust- 
chamber.  The  number  of  middlings  grades  here  is  three,  and  the  number 
of  fannings  two,  though  four  to  six  floors  of  k  could  be  made,  and  then 
four  to  six  aspirations  would  be  obtained. 

The  theoretic  problem  of  motion   of  the  particles  for  this  type   of 


FIG.  388. 


Fio.  389. 


purifier  is  most  simple,  but  the  introduction  into  the  machine  of  a  con- 
structive device  in  the  shape  of  gyrating  discs  rendered  it  considerably 
more  complicated  ;  that  type  of  purifier  is  therefore  quite  extinct  now. 

With  this  the  history  of  the  first  period  of  development  of  purifier 
may  be  concluded.  Beginning  with  the  eighties  of  the  last  century,  the 
machines  for  grading  the  stock  according  to  quality  begin  to  develop 
into  another  type. 


II 

MIDDLINGS-  AND  DUNST-GRADING  MACHINES  OF  TO-DAY 

After  the  series  of  modifications  in  the  constructions  of  machines  for 
grading  the  middlings  and  dunst  according  to  quality  recorded  above, 
modern  technics  fixed  upon  two  types  of  machines.  One  of  these  types 
retained  the  principles  of  Haggenmacher's  first  purifier,  which  in  Pro- 


CHAP.   Vl] 


FLOUR   MILLING 


407 


fessor  Zworykin's  terminology  was   called  "  self  purifier  "  ;  1   the  other 
is  a  machine,  in  which  the  product  moves  over  the  sieve.     The  air  passes 
through  the  sieve  and  lifts   the  light 
particles    of     stock.       This    type    of 
machines   Professor   Zworykin    names 
the  "  sieve  purifier." 

Haggenmacher  and  VolVs  Gravity 
Purifier. — The  latest  construction  of 
Haggenmacher's  gravity  purifier, 
patented  jointly  with  Voll  in  1907,  is 
designed  mainly  for  large  and  partly  for 
medium  middlings.  This  gravity  puri- 
fier is  always  set  to  work  in  conjunction 
with  the  middlings  grading  sifter,  and 
is,  therefore,  also  named  "  the  group." 

The  middlings,  graded  according  to 
size  by  the  sifter  into  from  eight  to  six- 
teen grades  (Figs.  390  and  391,  eight 
grades  of  middlings  in  all),  pass  into 
the  hoppers  A,  the  outer  wall  m  of 

which  is  a  self-adjusting  gate  with  a  weight  g.     The  feed  roll  a  feeds 
the  stock  in  an  even  stream  to  the  spreader  board  b,  in  sliding   over 


FIG.  390. 


_:z. 


FIG.  391. 
which  the   particles  of  middlings,  equal  in  size  but  unequal  in  weight, 

1  In  England  this  machine  is  known  as  the  "  gravity  purifier,"  in  contradistinction  to 
the  *'  sieve  purifier."     This  term  will  therefore  be  employed  in  the  text. 


408  FLOUR   MILLING  [CHAP,  vi 

acquire  different  velocities  of  motion.  Running  off  the  spreader  board, 
these  particles  have  various  speeds,  and  therefore,  when  meeting  a 
current  of  air,  give  different  deflections  from  their  initial  direction. 
Falling  in  accordance  with  their  quality  into  the  bottomless  feeding 
boxes  c,  the  middlings  pass  through  them  into  the  chamber  space, 
where  they  undergo  a  second  fanning,  after  which  the  cleaned  product 
drops  into  hoppers  d,  divided  according  to  quality.  Over  these 
hoppers  adjustable  valves  are  placed,  and  may  be  moved  to  the  right 
or  to  the  left,  according  to  the  force  of  the  draught  from  the  fan  and 
the  size  of  the  stock  graded.  From  the  hopper  d  the  graded  product 
runs  to  the  worms  and  is  discharged  by  them  from  the  machine. 

The  Double  Gravity  Purifier. — In  Figs.  392  and  393  is  shown  a 
double  gravity  purifier,  also  built  by  Haggenmacher  and  Voll.  The  stock 
falls  first  upon  the  top  sieve  S  feeding  the  throughs  to  the  second  sieve 
and  the  tails  for  discharge.  The  second  sieve  S'  passes  the  smaller 
throughs  from  the  right-hand  side  half  to  the  corresponding  part  of  the 
purifier.  The  bolted  product  runs  into  the  hoppers  A,  whence  it  is 
delivered  by  feed  rolls  a  to  the  spreader  boards  b.  On  the  way  from  the 
spreader  boards  b  the  stock  is  aspirated,  and  drops  to  the  bottomless 
boxes  c,  from  which  it  is  directed  into  boxes  d  in  streams  separated 
according  to  quality  and  size,  and  undergoes  fanning  once  more  on  its 
route.  The  boxes  d  have  adjustable  valves  e,  which  are  regulated 
in  accordance  with  the  size  of  the  stock  to  be  graded.  From  the  boxes  d 
the  graded  product  flows  to  the  discharge  spouts  /  for  further  treatment. 
Between  the  divisions  of  the  purifier  there  is  the  fan  chamber  in  which  the 
suction  fan  h  is  set. 

The  Haggenmacher  and  Voll's  machines  we  have  examined  are  de- 
scribed according  to  specimens  built  by  the  works  of  Dobrovyand  Nabholtz, 
but  the  same  type  of  machines  of  similar  principle  are  made  by  other 
works  also,  such  as  Daverio,  Luther,  Amme,  Giesecke  and  Konegen,  &c. 

Smith's  Sieve  Purifier. — Smith's  sieve  purifier  was  originally  invented 
in  America,  and  under  the  name  of  "  Reform  "  was  evolved  by  the  works 
of  Seek  Bros.  It  is  constructed  on  a  different  principle  of  action  to  that 
of  Haggenmacher 's  gravity  purifier,  which  originates  in  Ignatz  Paur's 
first  sieve  purifier. 

The  principle  of  action  of  that  sieve  purifier  is  as  follows  (Fig.  394) : 
If  we  compel  the  stock  to  travel  over  the  sieve  a-a  in  the  direction  pointed 
by  arrows  b,  and  at  the  same  time  impel  a  current  of  air  of  a  sufficient 
force  under  the  sieve,  the  state  of  the  flowing  product  will  be  similar  to 
that  of  boiling.  Its  light  particles  will  be  lifted  over  the  sieve  and  carried 


CHAP.    Vl] 


FLOUR   MILLING 


409 


410  FLOUK   MILLING  [CHAP.  Vi 

by  the  draught  upwards.  Part  of  that  light  refuse  will  be  sucked  out 
towards  the  fan,  the  rest,  consisting  of  heavier  offal,  will  collect  in  boxes 
over  the  sieve,  into  which  it  will  drop  owing  to  the  abatement  in  the 
velocity  of  the  air,  which  expands  on  leaving  the  canals  between  the  boxes. 

In  this  way,  the  air- current  here  lies  at  an  angle  of  180°  to  the  direction 
of  bolting,  and  at  an  angle  of  90°  to  the  direction  of  motion.  The  light 
particles  are  lifted  off  the  sieve  and  separated  as  light  or  heavy  offal.  The 
heavy  product  passes  through  the  sieve,  and  the  tails  consist  of  the  large, 
generally  less  heavy  product,  because  the  largest-sized  middlings,  the  con- 
ditions of  reduction  of  the  kernels  being  equal,  always  consist  of  the 
integumental  particles  of  grain.1 

The  principle  of  this  machine  has  remained  unchanged  up  to  the 
present  day,  and  on  this  principle  the  machines  are  designed  in  Europe 


FIG.  394. 

as  well  as  in  America.  In  some  constructive  minutiae  the  works  of  Seek 
Bros,  have  altered  their  "  Reform  "  purifier  from  their  first  model,  and 
in  its  present  shape  it  is  given  on  Figs.  395  and  396.  The  stock  to  be 
treated  flows  into  the  hopper  a,  and  is  then  fed  in  an  even  stream  by 
the  feed  roll  6  to  the  surface  of  the  sieve  c,  performing  a  reciprocating 
motion.  Above  the  sieve,  at  no  great  height,  are  set  similarly  to  fire- 
grates sheet-iron  channels  d,  with  their  ends  inclined  to  the  longitudinal 
channels/.  The  sieve  being  placed  in  a  closely  shut  up  chamber,  the  whole 
of  the  air  sucked  in  by  the  fan  e  must  pass  through  the  bolting  cloth. 
The  light  refuse  is  carried  away  by  the  fan  to  the  dust  collector, 
the  heaviest  falls  into  the  sheet-iron  channels  d  and  the  side  worm  (Abstoss 
der  Aspiration),  and  the  medium  refuse  upon  the  inclined  planes  lying 
over  the  channels  d.  The  refuse  collecting  inside  the  chamber  generally 

1  In  one  and  the  same  break  or  rebreak  passage  the  coloured  middlings,  i.e.  the  particles 
covered  with  bran,  are  always  larger  than  the  pure  ones.  This  is  due  to  the  fact  that 
the  middlings  with  offal  are  more  elastic,  and,  consequently,  offer  greater  resistance  to  reduc- 
tion than  middlings  out  of  the  pure  endosperm. 


CHAP.    Vl] 


MILLING 


411 


mixes  together,  whereas  the  offal  settling  in  the  worm  separates,  being  the 
heaviest  obtained  in  fanning  the  refuse  off  the  sieve  c. 

The    cleaning   of   the   sieve   c  is   performed   by  means   of   brushes 


'— Inlet. 


A— Refuse  from  ventilation. 


FlG.   396. 
L— Inlet  of  air. 


S_Overtails  of  sieve. 


u — Outlet  of  middlings. 


fastened  to  endless  chains.  The  transmission  of  motion  is  sufficiently 
clearly  illustrated  by  the  drawing. 

This  type  of  machine  operates  well  in  cleaning  different  sized 
middlings,  also  coarse  and  fine  dunst.  A  perspective  view  of  the 
machine  is  shown  on  Fig.  397. 

Robinson's  Sieve  Purifier.  -  -  The 
English  sieve  purifier  constructed  by 
Robinson  (Fig.  398)  is  also  a  modifica- 
tion of  Smith's  purifier,  but  in  its  prin- 
ciple of  action  it  remains  unchanged, 
as  do  also  the  sieve  purifiers  of  other 
works. 

/  illustrates  the  longitudinal  section 
of  this  purifier,  //  a  cross-section,  and 

///  and  IV  are  the  plans.  Figure  1  indicates  the  frame  of  the  oscillat- 
ing sieve,  2  its  bolting  surface,  3  the  deflecting  boards  V-shaped  at  their 
base.  The  air,  directed  upwards  and  aspirated  by  an  ordinary  fan  6, 
lifts  out  of  the  stock  on  the  sieve  2  the  light  particles  in  such  a  way,  that 
they  fall  upon  the  deflecting  boards  and  are  rejected  to  the  sides  of  the 


FIG.  397. 


412 


FLOUK   MILLING 


[CHAP,  vi 


bolting  tray,  where  the  greater  part  of  them  land  on  the  deposit  plat- 
forms 7.  When  several  trays  3  are  used  with  spaces  in  between  them, 
the  air-current  passing  through  the  sieve  2  is  equal  in  force  in  all  parts 
of  such  a  sieve.  The  trays  are  made  with  gravels  8  for  the  sake  of 
greater  lightness,  and,  owing  to  their  channelled  shape,  serve  for 
collecting  the  heavy  refuse,  which  has  a  tendency  to  falling  back  on  to 
the  sieve.  It  is  best  to  fix  the  trays  3  with  their  ends  to  the  frame  of 


FIG.  398. 

the  sieve  1,  so  that,  when  swinging,  the  dust  in  the  grooves  8  and  on  the 
side  channels  7  would  travel  to  the  lower  edge  and  fall  into  the  dust- 
collecting  box  9.  Figure  10  indicates  the  spout  conveying  the  stock  into 
the  working  space,  11  the  spout  for  overtails,  12  a  hopper  for  the  throughs, 
13  the  frame  of  the  machine.  If  the  air-current,  on  passing  by  the  de- 
flecting trays  3,  were  to  run  directly  to  the  fan  6,  part  of  the  offals 
would  not  settle  on  the  side  channels  7,  but  would  be  carried  to  the 
fan.  To  avoid  this,  the  direction  of  the  draught  blowing  by  the  trays  3 


CHAP.    VlJ 


FLOUR    MILLING 


413 


is  sharply  altered  by  means  of  the  baffle  plate  14  attached  to  the  frame  13. 
In  the  centre  of  the  baffle  plate  14  there  is  made  a  long  and  narrow  hole  15, 
parallel  to  the  spaces  between  the  deflecting  trays  3.  Thus,  all  the 
air  passing  between  the  trays  is  deflected  to  the  opening  15,  and  the 
greater  part  of  the  offals  settle  on  the  side  channels  7.  With  joints 


FIG.  399. — Cross  Section  of  Sieve  and  Channel  Cowl. 

17  under  the  hole  15  there  a-re  attached  adjustable  gates  16,  the  free  edges 
of  which  may  be  brought  closer  to  or  further  from  each  other  by  means 
of  rods  1 8  or  some  other  contrivance  for  regulating  the  width  of  the  open- 
ing. With  figure  19  is  indicated  the  deflecting  cap  over  the  opening  15, 
which  compels  the  remaining  particles  of  dust,  owing  to  the  centrifugal 
force  they  develop,  to  settle  on  the  top  side  of  the  baffle  plate  14,  whence 


FIG.  400. — Perspective  View  of  Channel  Cowl 
in  Working  Position. 


FIG.  401.— Channel  Cowl 
of  Sieve. 


they  may  be  removed  by  a  running  brush  or  in  some  other  way.  Having 
passed  the  baffle  plate  14,  the  exhausted  air  goes  through  the  passage  20  • 
to  the  fan  6.  This  fan  impels  the  air  along  the  passage  21  to  the  ex- 
pansion chamber  separator  22,  which  is  of  the  centrifugal  type.  In  the 
expansion  chamber  the  air  circulates  spirally  and  makes  its  exit  through 
the  outlet  23.  The  rest  of  the  dust  deposited  by  centrifugal  force  on  the 
casing  collect  in  the  dustbox  24,  whence  by  means  of  the  worm  25  jt  is 


414 


FLOUR    MILLING 


fCHAP.    VI 


taken  out  of  the  machine  or  conveyed  to  one  of  the  side  channels  7. 
Several  fans  and  separators  may  be  employed.  Fig.  IV  illustrates  on 
a  reduced  scale  the  plan  of  a  machine,  similar  to  the  one  examined,  but 
with  two  fans  6  and  two  dust  collectors  22. 

For  convenience  sake  when  using  the  sieve  purifier  for  coarse  pro- 
duct or  for' two  kinds  of  stock  with  a  stronger  current  of  air,  the  sieve  is 
divided  in  two  parts,  and  the  stream  of  product  is  guided  separately  to 
each  half.  Both  the  air-currents  are  directed  into  the  centrifugal  separa- 


FIG.  402. 

tor  and  the  fan,  as  in  the  former  case.  In  Fig.  402  is  given  the 
longitudinal  section  of  such  a  sieve  purifier.  The  parts  corresponding  to 
parts  /,  //,  and  ///  are  marked  with  the  same  figures.  The  sieves  2 
face  each  other  at  an  incline.  For  each  of  the  sieves  there  is  a  separate 
feeding  spout  10.  Number  11  indicates  the  deposit  platforms  for  refuse, 
•  and  9  an  ordinary  worm  for  refuse  rejected  by  deflecting  trays  and  the  side 
deposit  platforms  of  both  the  sieves.  The  dust  collector  22  is  furnished 
with  two  inlets  adjusted  by  the  valves  26,  so  that  through  both  the  sieves 
there  should  pass  air-currents  of  equal  force.  In  this  case  the  air  is  not 
impelled  through  the  collector,  but  drawn  through  it  by  the  fan  6  sta- 
tioned by  the  outlet  23.  The  offal  from  the  box  24  goes  to  the  worm  25? 


CHAP.    Vl] 


FLOUR   MILLING 


415 


416 


FLOUR   MILLING 


[CHAP,  vi 

which  conveys  it  out  of  the  machine.  Over  the  divisions  of  the  sieve 
there  may  be  set  boards  27  to  reduce  in  case  of  need  the  air-current  which 
passes  through  the  sieve  at  this  point,  where  the  strength  of  the  draught 
is  the  greatest. 

A  perspective  view  of  the  sieve  purifier  is  given  on  Fig.  403. 

Schneider,  Jacquet  cfc  Co.'s  Sieve  Purifier. — A  characteristic  pecu- 
liarity of  the  Schneider,  Jacquet  &  Co.  sieve  purifier  is  that,  firstly,  it 
requires  no  dust- collect  or  for  the  fan  offals,  and  secondly,  it  operates 
with  one  and  the  same  volume  of  air,  which  moves  in  the  machine  in  a 
locked  current. 

On  Figs.  404  and  405  may  be  seen  the  longitudinal  (the  middle  part 


FIG.  404. 


of  the  machine  is  cut  out)  and  transversal  sections.     The  action  of  the 
machine  is  as  follows. 

The  air  in  the  chamber  of  the  machine  is  brought  into  motion  by  the 
fan  a  with  an  outside  driving  belt-pulley  b.  From  the  fan  the  current 
of  air  passes  down  a  vertical  spout  to  a  horizontal  channel  c  (Fig.  405). 
Then  it  travels  as  indicated  by  the  arrow  through  the  longitudinal 
bottom  opening  d  of  this  channel  to  the  working  chambers  under  the 
sieves  and  returns  to  the  fan.  On  its  way  the  air  passes  through 
vibrating  sieves  e,  on  which  the  stock  to  be  purified  lies.  The  lighter 
particles  are  carried  off  the  sieve  by  the  air-current,  to  pass  through  the 
chambers  /  and  openings  g  into  the  separating  space  h.  In  travelling 
from  the  sieves  e  down  the  chambers  /,  the  current,  owing  to  their  de- 
creasing transversal  section,  becomes  narrower.  The  velocity  of  the 
draught  here  must  therefore  increase  ;  it  attains  its  largest  magnitude 
when  the  current  passes  through  the  openings  g,  and  then  it  all  at  once 


CHAP,  vi]  FLOUR    MILLING  417 

drops  to  its  minimum,  so  that  the  light  particles  carried  away,  losing  their 
kinetic  energy,  drop  into  the  chamber  of  the  worm  i.  The  increase  in 
the  velocity  of  the  air-current  when  passing  through  the  chambers  / 
is  an  advantage,  in  so  far  that  the  light  particles  separated  from  the 
stock  on  sieves  e  cannot  fall  back.  Owing  to  the  expansion  of  air  in  the 
collecting  space,  the  light  particles  settle  down,  and  are  thence  carried 
away  by  means  of  the  worm  conveyor  i.  The  air  chambers  /  are  so 
arranged,  that  the  openings  g  can  be  adjusted  by  the  valves  k. 

Each  machine  has  several  chambers  /  arranged  in  rows.  For  the 
stock  under  treatment  to  be  evenly  cleaned,  it  is  indispensable  that  the 
air  should  pass  through  all  the  chambers  at  an  equal  pressure.  The 
pressure  of  the  current  leaving  the  fan  and  running  into  the  channel  c 
decreases  when  passing  down  this  channel.  Because  of  this  difference  in 
pressure,  the  outlet  d  running  below  along  the  channel  c  is  made  wider 
behind  (from  the  fan)  than  in  front,  and  has,  in  this  manner,  the  shape  of 
a  trapezium.  Expelled  through  this  opening  in  the  channel,  the  air  flows 
out  with  an  even  pressure  at  every  point  of  the  passage,  and,  owing  to 
the  backward  increasing  width  of  the  openings  in  the  sieves  e,  blows 
through  the  working  chambers  with  different  force.  This  will  be  clearly 
explained  by  the  following. 

By  passing  through  the  outlet  in,  the  channel  c,  the  air  acts  upon  the 
reverse  surface  of  all  the  sieves  e  with  equal  pressure.  Since  the  stock 
to  be  purified  lies  in  a  large  mass  on  the  first  sieve,  which  is  finely  meshed, 
the  purifying  draught  of  air  cannot  pass  through  this  layer  of  product 
as  easily  as  through  the  more  open  back  sieves  where  the  layer  of  product 
has  already  been  partly  bolted,  and  is  consequently  not  so  thick.  The 
quantity  of  air  passing  through  the  front  sieve  is  therefore  the  least,  and 
in  proportion  as  we  approach  the  last  sieves  it  increases,  since  the  re- 
sistance to  be  overcome  by  the  air-current  in  passing  through  a  suc- 
cessive row  of  sieves  with  decreasing  numbers  gradually  diminishes. 
Thus  the  grading  air-current  penetrates  all  parts  of  the  machine  with 
equal  pressure,  but  through  the  working  chambers  /,  owing  to  the  dimin- 
ishing resistance,  the  air  passes  in  different  quantities.  Owing  to  this, 
the  process  of  purification  is  performed  evenly  in  all  the  air  chambers, 
because  the  draught  penetrates  into  them  with  equal  pressure. 

Down  the  inlet  boss  I  (Fig.  404)  the  stock  to  be  graded  runs  in  a  manner 
required  to  the  vibrating  sieves  e  in  the  machine,  over  which  it  travels 
in  a  longitudinal  direction.  At  the  boss  ra  the  coarser  parts  which 
have  not  passed  through  the  sieve  meshes  are  tailed  over.  The 
middlings  which  passed  through  the  meshes  into  the  box  n  are  carried 

2D 


418 


FLOUR    MILLING 


[CHAP,  vi 


away  by  worm  conveyors.  To  allow  of  the  frequent  inspection  of  the 
purification  during  operation,  in  the  chambers  /  there  are  windows  o 
adapted  especially  for  that  purpose.  The  even  distribution  of  the  air- 
current  in  the  whole  machine  down  the  channels  c  and  h  has  this  advantage, 
that  the  fine  light  particles  are  not  carried  by  the  draught  to  the  chambers, 
but  settle  in  a  special  compartment.  The  chief  chamber  for  the  precipita- 
tion of  the  light  particles  h,  which  also  runs  down  the  length  of  the 


l 


FIG.  406. 


machine,  is  to  this  end  divided  by  suitably  adapted  partitions  p  into  a 
certain  number  of  sections,  so  that  each  two  opposite  inlets  of  the  cham- 
bers g  open  into  one  such  section.  The  partitions  do  not  cut  off  the  chamber 
h  in  its  full  height,  so  that  the  light  particles  of  product  settling  in  all  the 
sections  may  be  discharged  by  means  of  a  common  worm  conveyor  i. 

The  surfaces  on  which  the  particles  separated  from  the  stock  preci- 
pitated are  so  arranged  that  these  particles  cannot  remain  settled  any- 
where, and  are  constantly  delivered  by  the  machine  as  heavy  offal. 


CHAP. 


FLOUR   MILLING 


419 


Thus  the  peculiarities  of  this  middlings  and  dunst  purifying  machine 
consist  in  that  under  the  chamber  h  for  collecting  the  light  particles  of 
product  passing  down  the  full  length  of  the  machine  there  is  arranged  a 
channel  c,  for  the  passage  of  air,  which  also  runs  through  the  length  of  the 
machine.  The  longitudinal  bottom  opening  d  of  this  channel  is  arranged 
to  correspond  to  the  decrease  in  pressure  in  such  a  manner  that  the  air- 
current  passing  out  of  it  enters  all  the  working  chambers  at  an  equal 
pressure. 

The  chamber  h  for  the  light  particles  is  divided  by  partitions  into 
several  sections,  the  number  of  which  corresponds  to  the  number  of 
double  chambers  /.  This  is  done  to  prevent  the  formation  of  strong  air- 
currents  in  the  narrow  part  of  the  chamber  h  about  the  inlets  g. 

Fig.  406  illustrates  the  perspective  view  of  the  sieve  purifier. 

H.  Brunner's  Purifier. — In  his  recently  patented  machine  Brunner 
aims  at  a  simplification  in  the  construction  of  the  types  we  have  ex- 
amined, attempting  to  dis-  i  j  0  6 
card  the  collecting  plates  '  p'-rfekT...,  ,-j^— ^"^4^1^  ^^ 
and  worms  from  the  purifier. 
His  point  of  departure  was 
the  principle  that  with  the 
decrease  in  the  cross  section 
of  the  passage  of  air  over 
the  sieve,  the  velocity  of 
motion  of  the  offal  increases 
and  their  falling  back  on  the 
sieve  is  an  impossibility. 
In  all  the  constructions 
illustrated  in  Figs.  407-410  the  air  from  the  chamber  a  occupying  the 
full  length  of  the  sieve  is  drawn  out  by  a  suction  fan.  Through  the  open- 
ings adjusted  by  gates  b  the  air  passes  out  of  the  chamber  c,  which  is 
divided  into  several  parts.  The  space  c  containing  the  rarefied  air  contracts 
after  this,  beginning  immediately  from  the  sieve  d,  owing  to  which  the 
air-current  is  evenly  distributed  over  the  full  breadth  of  the  sieve.  In 
Figs.  408  and  409  the  contraction  of  the  space  c  is  attained  by  having 
the  walls  e  and  /  raised  in  the  shape  of  a  cone  upwards  from  the 
sieve.  In  Fig.  410  are  illustrated  the  intermediate  partitions  g  built 
into  c,  which  also  assist  in  making  that  space  rapidly  narrower,  so 
that  directly  it  leaves  the  sieve  the  air -current  acquires  a  greater 
speed  and  the  light  particles  lifted  are  carried  away  to  the  outjets  b 
and  through  their  openings  pass  into  the  chamber  a.  The  bottom 


FIG.  407. 


FIG.  408. 


FIG.  409. 


FIG.  410. 


420  FLOUR   MILLING  [CHAP,  vi 

of  the  chamber  a  may  be  slanting,  and  then  the  heavy  refuse  will 
run  out  of  itself  ;  or  the  draught  may  also  be  left  there  of  such  force 
that  it  would  be  able  to  carry  these  particles  out  of  the  chamber  with  it. 
In  the  second  case  the  heavy  refuse  can  be  collected  by  the  dust-  collect  or 
or  in  some  other  way. 

Ill 

CAPACITY  OF  PURIFIERS 

In  his  book  Professor  Zworykin  gives  the  capacity  of  the  purifiers  in 
accordance  with  the  length  of  the  working  air  fissure. 

Let  us  name  the  capacity  of  the  machine  Q,  the  length  of  the  fissure  b, 
the  velocity  of  motion  of  the  product  v,  and  the  width  of  the  fissure  (the 
thickness  of  the  stream  of  product)  e.  Then  we  obtain  : 

Q  =  abev, 
where  a  is  the  coefficient  of  proportionality. 

If  we  name  the  finished  stock  $0,  it  may  be  expressed  through  Q  by  in- 
troducing the  coefficient  of  proportionality  k,  which  is  the  number  of  pas- 
sages required  for  cleaning  the  product  : 


«=k  =  —  •  -  •  ;•  •  •.  •  •     - 

But  k,  the  number  of  passages,  is  proportionate  to  the  thickness  of 
the  sheet  of  product  fed  in  and  inversely  proportionate  to  its  average 
dimensions.  Therefore 


where  ft  is  the  coefficient  of  proportionality.  But  k,  the  number  of  pas- 
sages, will  diminish  with  the  increase  of  the  number  of  fannings  n. 
Therefore  : 


By  substituting  k  from  (2)  into  (1),  we  obtain  : 


Since  practice  shows  that  almost  in  all  constructions  of  purifiers 
the  velocity  of  the  feed  is  a  constant  quantity,  we  finally  obtain  : 

Qo=Abdn (3), 

i.e.  t^e  capacity  of  the  purifier  is  directly  dependent  on  the  length  of  the 
fissure,  the  size  of  the  stock  treated,  and  the  number  of  fannings. 


CHAP.   Vl] 


FLOUR   MILLING 


421 


Experiments  show  that  1  cm.  of  total  length  of  the  draught  fissures 
produces  from  1  to  |  klg.  per  hour  or  54  to  27  Ib.  per  day  (24  hours)  of  pure 
semolina,  depending  on  the  size  of  the  product. 

These  data  refer  to  Haggenmacher's  type  of  purifier.  As  to  the 
purifier  of  Seck's  type  ("Reform")  this  calculation  is  useless,  for  the 
air-current  operates  through  the  sieve.  For  the  sieve  purifiers  it  would 
be  necessary  to  reckon  the  cross  section  of  the  "bolting  cloth,  lowering 
it  by  a  certain  coefficient,  because  the  stock  passing  through  the  sieve 
blinds  the  meshes  of  the  cloth  for  the  moment. 

In  calculating  the  number  of  purifiers  one  may  use  the  data  of  the 
works,  which  deserve  full  confidence.  The  compound  Table  XLII  of 
the  capacities  of  the  "  Reform"  type  sieve  purifiers,  from  practice,  gives 
results  almost  similar  to  the  data  of  the  catalogues  of  the  German  works. 

TABLE    XLII 

CAPACITY  OF  SIEVE  PURIFIERS 


Dimensions  of 
Machine  Nos. 

Working  Surface  of  the 
Sieve  on  an  Average  (for 
Different  Works)  in  Square 
Metres. 

Capacity  per  Hour  in  Cwts. 

Number  of  Vibra- 
tions (Double)  of 
the  Sieve  per 
Minute. 

Middlings. 

Dunst. 

1 

1-200-1-400 

11-8-16-0 

7-8-9-6 

500 

2 

1-000-1-200 

10-0-13-2 

5-9-8-2 

500 

3 

0-800-1-000 

8-1-11-0 

4-8-6-0 

500 

4 

0-500-0-640 

5-9-7-8 

3-2-4-5 

500 

5 

0-350-0-400 

3-6-5-1 

2-1-3-0 

500 

On  an  average  it  may  be  reckoned  that  1  square  metre  of  the  sieve 
purifier  cleans  10  cwt.  of  middlings  and  6  cwt.  of  dunst  per  hour. 

In  closing  the  section  on  grading  the  product  according  to  the  quality, 
we  must  point  out  that  a  gravity  purifier  of  Haggenmacher's  type  may 
be  employed  for  semolina,  and  sieve  purifiers  of  the  "  Reform  "  type  are 
preferable  for  cleaning  fine  middlings  and  dunst,  these  machines  being 
of  a  more  delicate  structure. 


CHAPTER    VII 

ACCESSORY  APPLIANCES  AND  MECHANISMS 

COMPARATIVELY  recently,  to  the  fundamental  mill  machinery  there  have 
been  added  a  series  of  appliances  and  mechanisms  of  an  accessory  char- 
acter, without  the  assistance  of  which  the  milling  process  would  be 
impeded  or  would  produce  unfavourable  results  in  respect  to  the 
quality  of  the  product  as  well  as  the  health  of  the  staff  operating  the 
mill. 

The  development  of  automatic  grinding  required  an  improvement  in 
the  transportation  service  at  the  mill,  and  the  necessity  for  keeping  a 
certain  standard  of  flour  on  the  market  compelled  millers  to  employ 
machines  and  apparatus  with  the  aid  of  which  the  influence  of  the  in- 
constancy in  the  quality  of  wheat  upon  the  outward  appearance  of  the 
flour  might  be  neutralised  to  a  certain  degree. 

The  most  essential  necessity  for  a  mill  is  the  ventilation  of  the 
machines.  By  means  of  exhausting  the  grain-cleaning  machines,  as  we 
saw  when  studying  their  construction,  the  removal  of  dust  and  screenings 
is  attained,  which  is  indispensable  not  only  for  the  machines,  but  for  the 
mill  building  as  well,  since  the  penetration  of  dust  into  the  parts  in  con- 
tact with  the  machine  is  injurious  to  them,  not  to  speak  of  the  danger  of 
explosions,  fires,  and  injury  to  health. 

In  the  mill  proper  the  ventilation  of  machinery  is  of  still  greater 
importance,  because  not  only  dust  but  evaporation  occurs  here.  In 
fact,  owing  to  the  heat  generated  by  grinding,  the  water  contained  in  the 
grain  turns  partly  to  steam,  especially  in  the  milling  of  soft  kinds  of  rye 
and  wheat.  The  heated  air,  saturated  with  steam,  comes  in  contact 
with  the  cold  walls  of  the  machines  and  bedews  them.  This  phenomenon 
is  identical  to  the  sweating  of  cold  window  panes  when  they  are  breathed 
upon.  In  the  winter,  the  formation  of  dew  in  the  machinery  of  the  mills 
with  badly  arranged  ventilation  is  so  great  that  the  water  pours  down  the 
inner  walls  of  the  roller  mills  in  thin  streams. 

Besides  the  machines,  the  spouts,  elevators,  worm  conveyors,  and 
bins  suffer  from  the  warm,  damp  air.  The  timber  parts  rot,  and  the  iron 
rusts.  The  flour  turns  to  paste,  clots  of  dough  block  the  spouts,  find  their 

422 


CHAP,  viz]  FLOUR    MILLING  423 

way  into  the  elevators,  and  thence  into  the  bolting  machines,  the  sieves 
of  which  become  blinded  by  the  paste,  and  the  capacity  of  the  mill  often 
drops  50  per  cent.,  and  sometimes  the  spouts  and  the  elevators  are  so 
badly  choked  that  it  is  necessary  to  stop  the  mill  and  give  the  machines, 
spouts,  and  elevators  a  general  cleaning. 

The  damp  air,  however;  has  a  detrimental  effect  not  only  upon  the 
machines,  but  upon  the  meal  too.  The  moisture  contained  by  the  flour 
imparts  a  dark  colouring  to  it.  If  the  flour  contains  a  great  quantity  of 
moisture,  a  spirituous  fermentation  often  sets  in,  and  reduces  its  rising 
and  baking  qualities. 

Thus,  the  aim  of  ventilation  is  to  remove  the  dust  and  the  warm, 
damp  air  from  the  machines. 

In  classifying  the  accessory  appliances  and  mechanisms  in  the  mill 
we  may  divide  them  into  two  groups  : 

I.  Ventilation  of  the  machinery  and  the  mill. 

II.  Transportation,  blending,  and  improvement  of  the  product. 
The  first  group  gives  the  following  two  sub -divisions  :  - 

1.  Mechanisms    and    apparatus    for    improving    the    intermediate 

products. 

2.  Dust-collectors. 

The  second  group  has  four  sub -divisions  : 

3.  Transportation  of  the  stock. 

4.  Apparatus  for  blending  the  flour  and  packing. 

5.  Apparatus  for  calculating  the  quantity  of  stock. 

6.  Apparatus  for  bleaching  the  flour. 

In  this  order  we  shall  now  proceed  to  examine  the  construction  of 
the  accessory  mechanisms  and  apparatus. 

I 

PURIFICATION  or  THE  INTERMEDIATE  PRODUCTS 
Robinson's  Cyclo-pneumatic  Separator. — This  separator  is  placed  after 
the  break  rolls  for  the  first  four  or  five  breaks.  We  know  that  a  certain 
small  percentage  of  bran  is  reduced  to  meal  dust  and  stripped  off  the  berry 
in  the  shape  of  small  beeswing  on  the  grain  being  passed  through  break  rolls. 
In  addition,  part  of  the  remaining  beard  is  torn  off,  and  broken  up. 
The  integumental  dust  darkens  the  break  flour,  the  offal  mixes  with  the 
middlings,  and  the  hairs  of  the  beard  blind  the  meshes  of  the  meal  sieves 
and  make  sifting  difficult.  To  separate  the  bran  powder,  offal,  and 
beard,  it  is  well  to  employ  apparatus  through  which  the  break  product 
can  be  passed  and  subjected  to  cleaning.  Robinson's  separator 


424 


FLOUR   MILLING 


[CHAP,  vii 


(Fig.  411)  is  such  an  apparatus.  It  is  a  cyclone  and  an  aspirator  com- 
bined. The  break  product  runs  from  the  rolls  into  the  feed  tube  D  and 
through  it  on  to  the  rotating  disc  A,  which  flings  the  product  up  fanwise. 
On  its  route  from  the  space  E  to  the  hopper  F,  the  product  is  subjected  to 
the  action  of  an  air-current  which  carries  away  the  dust,  offal,  and  bees- 
wing. Out  of  the  hopper  F  the  cleaned  break  chop  flows  down  the  spout 
G  into  the  sifter  for  further  grading. 

The  aspiration  is  effected  in  the  following  manner.  The  fan  W  sucks 
the  air  out  of  the  cyclone  into  the  space  E  and  drives  it  down  arrows  S 
into  the  chamber  B.  When  the  air  is  passing  out 
of  the  right-hand  side  part  of  the  chamber  into 
the  left  under  the  dividing  partition  L,  the 
heavier  particles  of  integument  develop  a  cen- 
trifugal force  and  fall  into  the  worm  P,  and  the 
air  with  the  lighter  dust  particles  flows  into  the 
cyclone.  The  centrifugal  force  presses  these  light 
particles  of  dust  against  the  walls  of  the  cyclone, 
and  they  roll  down  arrows  S  into  the  worm, 
while  the  pure  air  is  again  drawn  up  to  the  space 
E.  In  this  way  the  work  is  performed  by  a  con- 
stant quantity  of  air.  The  offal  from  the  chamber 
B  and  the  cyclone  collects  generally  in  a  common 
worm,  and  is  discharged  as  indicated  by  arrow  I. 
The  dust  offal  contains  also  a  part  of  break 
flour,  which  is  then  separated  away  on  a  sifter. 
To  prevent  any  circulation  of  air,  there  are  leather 
partitions  set  in  the  worm. 

The  Schneider,  Jacquet   &  Co.  Apparatus. — A 

more  simple  apparatus  for  cleaning  the  break  stock  is  the  chamber 
illustrated  on  Figs.  412,  413,  and  414. 

This  apparatus  is  stationed  before  the  break  rolls,  and  separates  the 
offal  from  the  break  semolina.  If  the  break  process  has  high  breaking 
and  eight  breaks,  it  is  well  to  set  the  apparatus  for  the  semolina  from  the 
first  (after  the  high  breaking)  six  breaks  and  for  the  rebreaks  (for  the  first 
two  of  the  three). 

Fig.  412  gives  the  longitudinal  and  half  of  the  transversal  section  of 
this  apparatus,  which  consists  of  a  rectangular  timber  cupboard,  through 
which  there  pass  the  worms  a  and  a±  for  the  removal  of  the  more  or  less 
heavy  offal.  The  break  semolina  flows  down  the  spout  A  on  to  the  in- 
clined plate  B.  On  this  plate  there  are  set  the  distributors  b,  which  break 


FIG.  411. 


CHAP.    VIl] 


FLOUR   MILLING 


425 


up  the  narrow  stream  of  product  into  a  broad  sheet,  which  descends  as 
shown  by  the  arrow  c  to  the  outlet  into  the  box  D  over  the  roller  mill. 
On  its  route  of  descent  the  product  is  subjected  to  the  action  of  an  air- 


FIG.  412. 


current  x  streaming  in  through  the  crevice  between  the  adjustable  gates 
d  and  d^.  Besides  the  regulation  of  the  width  of  the  crevice  between  the 
gates  d  and  dl9  the  force  of  the  draught  may  be  altered  by  the  gate  0.  The 
air  is  aspirated  by  a  fan  through  the  spout  E. 

The  longitudinal  and  the  side  view  of  the  installation  of  eight  machines 


FIG.  413. 


FIG.  414. 


is  shown  on  Figs.  413  and  414,  where  it  is  seen  that  the  offal  passes  into 
the  aspirated  worm  A,  whence  it  is  conveyed  tq  the  sack  or  to  the  bolt- 
ing machines. 

The  Briddon    &   Fowler  Pneumatic  Scalper. — Attempts   have   often 
been  made  to  arrange  the  cleaning  of  the  break  chop  in  the  roller  mill 


426  FLOUR   MILLING  [CHAP.  Vit 

itself,  but  with  no  good  result.  Of  the  latest  attempts,  a  construc- 
tion of  the  Briddon  &  Fowler  works  in  Manchester  (Fig.  415)  deserves 
attention. 

This  has  been  made  the  foundation  of  a  system  (patented)  of  milling. 
It  is  the  outcome  of  experiments  made  by  Fowler  in  a  Yorkshire  mill. 
He  found  that  a  pronounced  natural  separation  takes  place  in  break 
stock  coming  from  the  nip  of  diagonal  rolls.  The  heavier  stock,  i.e. 


FIG.  415. 

partly  broken  wheat,  semolina  and  heavy  middlings,  are  thrown  farthest 
from  the  roll,  while  the  break  flour,  finest  middlings  and  dunst  are  thrown 
down  on  the  inside.  An  adjustable  division  board,  under  the  nip  of  the 
rolls,  effects,  without  any  mechanical  agency,  an  immediate  separation  of 
the  heavy  and  the  branny  particles  from  the  floury  stock  and  fine  dunst. 
Thus  contamination  of  the  break  flour  or  the  production  of  inferior  attri- 
tion flour  is  obviated,  and  the  colour  and  granularity  of  the  break  flour 
are  improved.  Currents  of  air— working  as  in  a  gravity  purifier — assist 
the  separations.  The  system  is  working  most  successfully  in  many  of 
the  largest  British  mills,  and  is  regarded  as  one  of  the  most  successful 
innovations  of  recent  years. 

II 

DUST-COLLECTORS 

Dust-chamber. — The  simplest  kinds  of  dust-collectors  are  dust-cham- 
bers or  dust-bins.     Their  arrangement  is  very  simple.     A  free  corner  of 


CHAP,  vn] 


FLOUR   MILLING 


427 


the  mill  is  partitioned  off  by  a  timber  frame  clothed  with  canvas  (a 
simplified  chamber  is  clothed  with  old  flour  sacks),  thus  forming  a  dust- 
bin. The  dusty  air  is  driven  out  of  the  machines  by  fans  into  this  cham- 
ber, and  oozes  through  the  canvas  walls  of  the  bin,  leaving  the  dust  on 
them.  In  proportion  as  the  dust  collects  on  it,  the  canvas  is  shaken, 
the  dust  falls  on  the  ground,  and  is  removed  when  the  fan  stops  working. 
Sometimes  the  dust-bin  is  made  with  an  inclined  bottom  and  discharge 
spout  with  a  sack  fitted  to  it  to  receive  the  dust. 

This  simplest  kind  of  dust-collector  is  arranged  in  small  mills   with 


FIG.  416. 


FIG.  417. 


the  means  about  them.     The  dust-chamber  occupies  much  room,  but  its 
filtering  area  is  insignificant. 

Cyclones. — The  cyclone  apparatus  invented  by  the  Americans  is  a 
more  perfect  dust-collector.  On  Fig.  416  is  shown  an  ordinary  kind  of 
a  cyclone,  its  partial  section  and  the  view  from  the  top.  The  dusty  air 
flows  into  the  feeding  tube  A,  passing  into  the  ring  space  between  the 
cylindric  part  E  of  the  cyclone  and  the  outlet  tube  C.  This  ring  space  is 
covered  over  with  a  lid,  in  consequence  of  which  a  rotary  motion  is  im- 
parted to  the  air  in  the  ring  closed  on  the  top,  and  it  travels  in  a  helical 


FLOUR   MILLING 


[CHAP,  vn 


direction  downwards  along  the  arrow  8.  With  the  increase  of  resistance 
to  motion  the  air-current  in  the  narrowest  part  of  the  cone  is  impelled  in 
the  direction  of  least  resistance,  i.e.  upwards,  and  passes  out  through  the 
tube  C.  Owing  to  the  spiral  motion  of  the  air  the  particles  of  dust  de- 
velop a  centrifugal  force  and  press  against  the  walls  of  the  cyclone,  down 
which  they  slide  to  the  exit  B  influenced  by  their  gravity.  Thus,  the  air 
emitted  through  C  is  perfectly  pure  and  free  of  dust. 

Such  is  the  action  of  all  cyclones.  This  apparatus  is  very  simple,  its 
action  is  satisfactory,  but  it  is  comparatively  bulky. 

Wishing  to  improve  the  action  of  the  cyclone,  Howes'  works  in  America 
suggested  a  more  complex  construction  of  an  apparatus  with  a  com- 
pulsory spiral  motion  of  the  air  and  dust  in  the  chamber  (Fig.  417)  by 
furnishing  it  with  helical  arms.  This  complication  in  the  construction, 


FIG.  418, 


FIG.  419. 


FIG.  420. 


however,  does  not  improve  the  action  of  the  cyclone,  but  the  contrary, 
for  the  arms  have  very  little  influence  on  the  direction  in  which  the  air 
travels,  and  at  the  same  time  retard  the  delivery  of  the  dust. 

The  Knickerbocker  Co.  Cyclone. — The  cyclones  we  examined  have  the 
defect  that  quite  a  considerable  part  of  the  pressure  is  lost  because  of 
meeting  at  a  fairly  large  angle,  as  we  see  in  Fig.  418,  the  air  flowing  into 
the  cyclone  and  gyrating  there.  To  avoid  any  intersection  of  the  air- 
currents,  the  celebrated  American  cyclone  works,  the  Knickerbocker  Co. 
(Jackson,  Michigan),  which  invented  the  first  cyclone,  suggested  in  1905  a 
new  principle  for  a  cyclone,  in  which  a  spiral  motion  is  immediately  com- 
municated to  the  inflowing  air,  as  it  is  shown  in  Fig.  419.  Here  the  axis 
of  the  efflux  of  the  air  does  not  coincide  with  the  axis  of  the  cyclone. 
The  meeting  of  the  air-currents  is  obviated  in  the  cyclone  of  such  a  con- 
struction. 

On  Fig.  420  may  be  seen  the  cylindric  part  of  such  a  cyclone.     The 


CHAP.    VII] 


FLOUR   MILLING 


429 


air  runs  into  the  receiver  A  and  along  the  arrow  L  passes  spirally  to  the 
partitioned-off  section  of  the  chamber  J.  The  spiral  direction  is  com* 
municated  to  the  current  by  the  walls  E  and  F.  The  first  wall  is  closely 
fitted  to  the  wall  M  of  the  cylinder,  while  between  it  and  the  wall  F  there 
is  a  clearance  H  through  which  the  superfluous  amount  of  air  can  pass 
out  along  the  arrow  Llf  The  current  of  air  L  acts  partly  as  in  the  de- 
flector in  respect  to  the  chamber  J,  consequently  the  streams  L  and  Ll 
do  not  cross  each  other,  but  coincide.  And  if  the  air  travelling  under 
the  walls  of  the  chamber  J  has  not  separated  away  the  whole  of  its  dust 
and  offal,  then,  in  passing  again  into  the  fresh  supply  chamber,  it  can  be 
totally  freed  of  admixtures.  The  exhaust  air  passes  out  through  the 
opening  D,  eccentrically  made  in  the  lid  of  the  cyclone.  The  position 
of  the  opening  D  may  be  namr^ 

altered,  since  the  ring  K  is 
eccentrically  set  in  the  lid. 
This  is  of  consequence  for  a 
correct  setting  of  the  air  out- 
let. The  cyclone  construc- 
tion we  have  just  examined  is 
the  best  of  all  existing  types 
of  these  dust-collectors. 

Filters. — The  most  gener- 
ally used  dust-collector  is  the 
tube  filter,  which  has  almost 
totally  driven  out  the  cyclone 
in  European  mills.  The 
tube  filter  is  convenient  in 
this  respect,  that  occupying 
little  space  it  gives  a  large 
working  surface. 

On  Fig.  421  we  have  a 
pressure  tube  filter.  It  consists  of  two,  generally  timber,  boxes,  A  and 
B,  the  chambers  of  which  communicate  with  each  other  by  linen  tubes. 
The  dusty  air  carried  by  the  fan  C  out  of  the  ventilated  chambers  passes 
into  the  top  chamber  A,  whence  it  is  distributed  to  the  tubes  and  filters 
through  the  cloth,  leaving  the  dust  on  its  inner  surface. 

From  off  the  tubes  the  dust  is  shaken  by  means  of  a  frame  D,  which 
has  a  wire  running  from  one  side  to  the  opposite  on  every  one  or  two 
rows  of  tubes.  The  distance  between  the  wires  being  less  than  the  dia- 
meter of  the  tubes,  the  latter  are  compressed.  The  frame  D  runs  up 


FIG.  421. 


430 


FLOUR   MILLING 


[CHAP,  vn 


and  down  uninterruptedly,  and  in  this  manner  shakes  off  the  dust, which 
falls  into  the  bottom  box  B.  The  frame  D  rises  and  falls  by  means  of 
four  chain  drives,  it  being  suspended  on  the  chains  a  by  means  of  straps  b. 
The  dust  fallen  to  the  bottom  of  the  box  c  is  scooped  away  by  scrapers  d 
which  run  down  the  full  length  of  the  box  and  are  brought  into  action 
by  a  chain  drive  g  inside  it,  and  is  thrown  into  the  worm  e,  whence  it  is 
delivered  through  the  outlet  spout  as  indicated  by  the  arrow  s. 

Fig.  422  illustrates  the  suction  filter,  which  differs  from  the  preced- 
ing in  that  it  is  enclosed  in  a  common  box.  In  the  first  case  the  fan 
should  be  placed  between  the  aspirated  machine  and  the  filter,  in  the 
second  after  the  filter.  In  this  manner  the  fan  sucks  the  air  out  of 

the  box  A.  The  dusty  air  which  is 
conveyed  into  the  top  box  by  the  air 
pipe  from  the  machines  precipitates 
into  the  tubes  and  filters  through  their 
cloth,  owing  to  the  air  in  the  box  A 
being  rarefied.  Consequently,  through 
the  fan  there  passes  pure  air. 

In  comparing  these  two  types  of 
filters,  we  must  speak  in  favour  of 
the  first  one  for  cheap  plants,  seeing 
that  firstly  its  construction  is  more 
simple,  secondly  it  requires  15  to 
20  per  cent,  less  power,  there  being  no 
such  resistance  to  the  outflow  of  the 
exhaust  air  as  we  see  in  the  suction 
filter  ;  thirdly  and  lastly,  its  opera- 
tion is  easily  supervised,  whereas  in 
the  suction  filter  the  shaking  frame 
is  hidden  in  the  hermetically  closed 
box  A.  The  latter  circumstance  could  be  obviated  in  the  suction  filters, 
if  a  glass  inspection  window  were  to  be  made  in  A  ;  but  for  some  reason 
or  other  none  of  the  works  do  it,  though  this  would  be  very  useful. 
Among  the  defects  of  the  pressure  filter  we  may  count  the  fact  that  the 
exhaust  air,  not  always  free  of  dust,  passes  directly  into  the  mill,  whereas 
in  the  suction  filter  it  is  discharged  by  the  fan  into  the  open,  and  the 
mill  does  not  remain  free  of  dust  if  the  filter  works  unsatisfactorily. 

On  Figs.  423  and  424  may  be  seen  the  American  tubular  filters  made 
by  S.  Howes'  works.  The  first  one  is  a  type  similar  to  the  European 
construction,  differing  from  it  only  in  the  greater  ease  it  affords  for  inspec- 


FIG.  422. 


CHAP,  vn] 


FLOUR    MILLING 


431 


tion  of  the  lower  working  box,  the  lid  of  which  may  be  lifted.  The 
second  filter,  likewise  sectional,  is  more  simplified,  the  scrapers  here  being 
discarded  and  a  bin  with  a  worm  below  placed,  into  which  the  shaken-off 
dust  falls  out  of  the  outermost  tubes  down  the  inclined  walls  of  the  bin. 
The  star-shaped  forcing  filters  are  much  more  popular  in  America. 
Fig.  425  shows  such  a  filter,  made  in  Europe  by  Luther's  works.  The 
filter  consists  of  a  stationary  cylindric  casing  with  longitudinal  or  round 
holes.  Over  this  casing  is  fitted  another  similar  one,  but  rotating  with 
the  aid  of  a  ratchet  wheel  gear.  On  the  rotating  casing  there  is  set  a 
series  of  tubes  stretched  by  springs  on  either  end  of  the  plank,  which  is 
also  connected  with  each  tube.  The  driving  belt-pulley  is  the  large  one 


FIG.  423. 


FIG.  424. 


on  the  left ;  it  operates  the  whole  mechanism,  in  which  the  lever  pawl 
turns  the  filter  one  or  two  cogs,  while  the  hammers  on  the  axle  hit  the  tubes 
approaching  them  from  the  top.  Since  the  stationary  cylinder  is  divided 
into  two  parts,  of  which  the  lower  one  receiving  the  dusty  air  communicates 
through  the  holes  with  the  tubes,  and  the  top  one  containing  the  worm  is 
isolated  from  dusty  air,  the  dust  which  remains  after  the  air  has  passed 
through  the  cloth  of  the  lower  tubes  falls  out  of  the  top  ones,  when  they 
are  hit  with  the  hammers,  to  the  lower  part  of  the  casing,  and  is  dis- 
charged by  the  worm. 

In  spite  of  the  comparative  complexity  of  the  mechanism  these  filters 
are  very  widely  used,  owing  to  their  being  more  compact  than  the 
European  tubular  filters.  They  have  made  their  appearance  in  Europe, 
too,  of  late. 

We  shall  end  the  chapter  treating  of  filters  with  a  description  of 


432 


FLOUR   MILLING 


[CHAP,  vn 


one  of  the  latest  types  of  Seck's  suction  tubular  niters.  Fig.  426  illustrates 
the  longitudinal  and  the  cross  section,  and  Fig.  427  a  perspective  view 
of  this  filter.  It  consists  of  an  iron  cylindric  chamber  b  containing  the 
filtering  tubes  c  closed  at  the  top,  and  attached  by  their  edges  to  the 
bottom  of  the  chamber  and  open  for  the  discharge  of  dust.  With  the 
aid  of  an  aspirating  air  pipe  k  the  chamber  b  communicates  with  the 


6.  LUTHER  A.-6.  BRAUNSCHWEIG 


FIG.  425. 


fan.  The  dusty  air  from  the  exhausted  machines  passes  through 
the  air  pipe  i,  whence  it  runs  into  the  tubes  e  and  filters  out,  free 
of  dust,  into  the  chamber  b  owing  to  the  rarefaction  of  space  between 
the  tubes  and  the  casing  of  the  chamber.  The  tubes  are  suspended 
to  the  lever  d,  which  rises  and  falls  owing  to  the  operation  of  the 
ratchet  wheel  e  on  the  shaft  /.  Simultaneously  with  the  dropping  of 
the  lever  d,  during  which  the  tubes  receive  a  shake,  the  valve  /  also 


CHAP.    VII] 


FLOUR   MILLING 


433 


closes  automatically,  so  that  the  suction  of  the  air  out  of  the  filter  is  dis- 
continued for  the  moment  of  the  shake.  The  dust  descends  to  the  box  g, 
whence  it  passes  into  the  worm.  The  heavy  offal  drops  into  the  worm 
when  the  air  flows  into  g,  because  owing  to  the  sharp  curve  the  current 
performs  the  offal  develops  a  great  centrifugal  force  and  is  flung  down. 


FIG.  426. 

.  n—  Recurrent  of  air. 
S— Dust-laden  air. 


J 


FIG.  427. 

Generally  the  suction  filter  plants  have  two  chambers  at  the  very  least, 
as  in  Fig.  427.  But  more  often  three  or  four  chambers  are  joined 
together.  This  guarantees  continuous  work  of  the  filter  also,  because 
when  one  of  the  filters  is  being  cleaned,  i.e.  the  suction  tube  k  is  closed 
with  the  valve  I,  the  others  at  the  same  time  are  open,  the  ratchets  e 
being  brought  into  action  by  turns. 


434  FLOUR    MILLING  [CHAP,  vn 

III 

EXHAUST  SYSTEMS 
1.  Group  Exhaust  Systems 

Ventilation  of  Roller  Mills. — The  removal  of  the  bran  powder  and 
flour  dust,  as  well  as  the  cooling  of  the  rolls  and  of  the  heated  product,  is 
the  aim  of  ventilation  for  roller  mills.  There  are  two  ways  of  exhausting 
the  rolls.  The  first  is  based  on  the  principle  of  counter-currents,  when 
the  draught  is  directed  opposite  to  the  motion  of  the  product ;  the  second, 
when  the  direction  of  the  air  and  the  stock  coincide.  In  most  cases  the 
first  method  is  accepted  by  the  works,  by  reason  of  the  dust  being  easily 
separated  from  a  thin  sheet  of  product  with  an  air-current.  But  the 
condensation  of  steam  in  the  cooler  top  part  of  the  mill  chamber  and  the 
formation  of  paste  on  the  walls  of  the  frame  are  to  be  reckoned  among 
the  defects  of  this  method.  The  absence  of  condensation  owing  to  the 
constant  temperature  in  all  the  parts  of  the  chamber  speaks  in  favour  of 
the  second  method  ;  to  its  defects  may  be  referred  the  smaller  capacity 
of  the  air-current  to  remove  the  particles  of  dust  and  shells  from  the 
compact  mass  of  stock  travelling  down  the  spout  or  the  worm.  How- 
ever, the  defects  of  both  the  first  and  the  second  methods  are  avoidable. 
If  the  mills  are  not  overloaded  and  the  product  is  not  heated  much,  the 
difference  in  the  temperatures  will  be  insignificant  and  there  will  be  no 
condensation.  In  the  second  case,  when  the  air-current  crosses  the  sheet 
of  product,  the  particles  of  dust  are  extracted  out  of  it  and  do  not  mix 
in  the  spouts  with  the  rest  of  the  stock. 

Fig.  428  represents  an  American  ventilating  plant  on  the  principle 
of  counter-currents.  The  product  is  fed  in  at  S.  The  air  flows  into  the 
chamber  of  the  mill  through  the  windows  A,  which  are  covered  with 
cloth  or  a  metal  screen,  traverses  the  sheet  of  product  flowing  out  at  right 
angles,  and  passes  out  as  indicated  by  the  arrow  S±  into  the  common 
trunk  B,  carrying  the  dust  with  it.  The  fan  C,  in  sucking  the  air 
out  of  B,  forces  it  into  the  star  filter. 

On  Figs.  429  and  430  we  see  Seck's  system  of  exhausts,  in  which  the 
direction  in  which  the  product  travels  coincides  with  the  route  of  the  air. 
In  the  case  when  the  incline  of  the  spout  A  is  sufficient  for  the  product 
to  run  down  of  itself,  the  plant  in  Fig.  429  may  be  used.  The  product 
leaving  the  mill  flows  down  the  spout  A  to  the  elevator.  The  air  is  aspi- 
rated through  the  trunk  B,  which  directs  it  to  the  worm  C,  doing  service 
for  several  rolls,  and  whence  the  fan  sucks  the  air  through  the  trunk 
D,  In  the  spout  A  there  is  a  freely  suspended  valve  a,  which  does 


CHAP.    VII] 


FLOUR   MILLING 


435 


not  allow  the  air  to  pass  into  the  ventilated  worm  out  of  the  elevator  ;  in 
the  bend  of  the  trunk  B  there  is  a  valve  or  a  gate  b,  with  the  aid  of  which 
the  intensity  of  the  exhaust  in  any  particular  mill  may  be  regulated  by 
opening  it  wider  or  less.  The  heavy  offals  carried  away  by  the  air-current 


FIG.  428. 

out  of  the  stock  drop  into  the  worm  and  are  conveyed  by  it  into  the 
open,  while  the  light  dust  runs  down  the  trunk  D  to  the  filter,  where  it 
collects. 

In  case  the  elevators  have  to  be  stationed  far  from  the  roller  mills, 
and  the  stock  cannot  flow  to  them  of  itself,  the  exhaust  arrangement  shown 


436 


FLOUR   MILLING 


[CHAP,  vn 


in  Fig.  430  is  employed.  Here  is  set  the  worm  E,  out  of  which  the  air  is 
aspirated  by  a  similar  trunk  B.  In  the  remaining  part  of  the  plant  there 
is  no  difference. 

We  have  been  examining  here  the  exhaust  systems  of  the  most 
important  machines,  the  roller  mills.  Before  proceeding  to  a  description 
of  general  systems  of  exhaust  we  must  set  several  general  rules  for  a 
rational  construction  of  the  plants. 

How  important  a  correct  calculation  and  construction  of  exhaust  is 
we  may  judge  by  the  example  of  a  German  mill,  which  being  driven  by 
a  260  H.P.  steam  engine  consumed  110  H.P.  for  ventilation,  i.e.  43  per 
cent,  of  the  power  used  by  all  the  milling  machines.  Such  enormous 


FIG.  429. 


FIG.  430. 


consumption  of  power  for  the  exhausts  was  caused  solely  by  bad  con- 
struction and  incorrect  calculations. 

One  of  the  main  details  of  an  exhaust  plant  is  the  air  trunk,  down 
which  the  dusty  air  is  driven  out  of  the  machine  to  the  dust-collector  by 
means  of  a  fan  in  the  machine  itself  or  a  fan  outside  it.  The  separate 
air  trunks  communicate  with  the  main  trunk,  on  which  generally  the 
main  fan  is  set. 

In  constructing  and  reckoning  out  the  ventilation,  the  following 
general  rules  should  be  borne  in  mind  : 

1.  A  correct  computation  of  the  general  quantity  of  air  required  for 
the  plant  given,  i.e.  the  selection  of  suitable  fans. 

2.  The  sections  of  the  air  trunks  should  be  so  calculated  as  to  have  an 
equal  quantity  of  air  passing  in  their  different  sections,  where  the  velo- 
cities may  be  different. 

3.  The  coupling  of  the  air  trunks  should  be  such  as  to  involve  no  loss 
of  air  pressure. 


CHAP,  vii]  FLOUR   MILLING  437 

4.  The  dimensions  of  the  chambers,  cyclones,  and  filtering  surfaces 
ought  not  to  cause  any  superfluous  pressure,  which  requires  a  greater 
consumption  of  power. 

Rules  2,  3,  and  4  give  the  ground  on  which  a  correct  choice  of  the  fan 
can  be  made,  and  we  shall  therefore  speak  of  them  more  in  detail. 

If  we  have  two  equal  machines  placed  at  unequal  distances  from  the 
fan,  we  cannot  use  air  trunks  of  equal  sections.  Obviously  the  air 
trunk  of  the  further  machine  will  offer  greater  resistance  to  the  motion 
of  air,  being  the  longer  of  the  two.  To  have  both  the  machines  placed 
in  equal  conditions  of  ventilation,  it  is  necessary  to  make  the  trunk 
of  the  further  machine  larger  in  section,  taking  its  dimensions  in 
accordance  with  the  length,  which  defines  the  loss  in  pressure. 

In  no  case  may  trunks  of  an  equal  section  be  used  for  equal  machines, 
when  this  section  is  calculated  from  the  air  consumption  and  the  pressure 
of  the  machine  farthest  removed.  In  that  case  the  machines  lying 
nearer  to  the  fan  will  be  subjected  to 
a  more  energetic  exhaust  than  is  needed, 
and  the  regulation  of  the  air  trunks  by 
means  of  valves  or  gates  will  incur  an 
extra  consumption  of  power. 

The   absence   of    sharp  bends   in  the 

FIG.  431. 

trunks  and  their  joints  is  of  great  import- 
ance.    The  greater  the  number  of  bends,  especially  at  right  angles,  the 
greater  is  the  loss  in  pressure  of  the  exhaust  plant. 

The  coupling  of  air  trunks  must  in  no  case  be  at  right  angles,  as  we 
have  it  on  the  American  plant,  which  serves  as  an  example  of  the  worst 
kind  of  coupling  for  air  trunks.  If  we  have  a  coupling  of  two  air  trunks 
at  a  certain  considerable  angle,  about  45°  (Fig.  431),  for  instance,  then  the 
air-currents  b  entering  into  the  main  air  channel  intersect  with  the  cur- 
rents a  and  thus  hinder  each  other,  mutually  reducing  the  general  pressure. 
It  is  necessary  to  have  these  streams  almost  coincide  in  their  direction 
of  motion.  The  practice  of  to-day  has  fixed  the  largest  angle  formed  by 
the  axes  of  the  coupled  air  pipes  at  5°. 

As  to  the  size  of  dust-collectors  (chambers,  cyclones,  and  filters),  in 
selecting  them  such  dimensions  should  be  taken  as  will  not  cause  any 
loss  of  the  necessary  pressure  before  the  fan,  owing  to  stoppage 
of  the  exhaust  air  passing  out.  Beyond  these  limits  the  dimensions 
of  dust-collectors  may  be  increased  without  harm  to  the  plant  if  the 
space  and  the  means  allow  it.  Dust-collectors  of  super-normal  size 
facilitate  the  work  of  the  whole  plant. 


438 


FLOUK   MILLING 


[CHAP,  vii 


2.  General  Exhaust  Systems 

Ventilation  of  the  Grain-cleaning  Department. — Knowing  the  funda- 
mental requirements  of  a  rational  ventilation  of  machinery,  we  can  give 


FIG.  432. 

a  general  type,  as  a  more  complex  one,  of  an  exhaust  plant  for  the 
grain-cleaning  department  of  automatic  mills,  from  which  it  is  an  easy 
passage  to  simple  plants. 

On  Fig.  432  we  have  a  cross  section  of  the  grain-cleaning  department 
containing  all  types  of  machines.     The  ventilation  is  performed  by  means  of 


CHAP.    VII] 


FLOUR   MILLING 


439 


FIG.  433  and  FIG.  434. 


440  FLOUR   MILLING  [CHAP,  vii 

the  fan  A  and  the  suction  filter  B  of  the  Seek  type  we  have  ex- 
amined. The  main  air  channel  C  is  disposed  vertically,  and  tributary 
to  it  are  the  conveying  air  trunks  from  the  dusting  reel  separator  1, 
separator  2,  trieurs  3.  scourers  4,  brush  machines  5,  scouring  mill- 
stones 6.  clean  reel  separators  7,  and  lastly,  from  the  automatic  elevators 
8  at  two  points.  In  this  plant  we  see  that  the  junction  of  the  conveying 
trunks  with  the  main  channel  lies  at  the  least  possible  angle  of  their  axes. 
The  vertical  position  of  the  main  channel  is  to  diminish  the  quantity  of 
harmful  resistance,  and  the  fan  is  set  on  the  top  floor,  which  allows  of  utilis- 
ing the  natural  pressure  of  air  in  respect  to  the  machines  standing  below. 
Ventilation  of  the  Milling  Department. — In  Figs.  433  and  434  we  have 
a  diagram  of  the  exhaust  system  for  the  milling  department  of  a  rye 
mill  of  100  sacks  per  day  (24  hours)  capacity.  A 
fan  A  and  a  suction  filter  C  operate  for  this 
plant. 

Speaking   generally,   the   air   trunks    from    the 
b  machine  should  be  set   at  an  incline   allowing  the 

heavy  particles  settling  in  them  to  run  down  of 
themselves.  For  the  heavy  offals  to  run  down  in 
this  manner  it  is  sufficient  to  have  the  spout 
inclined  at  an  angle  of  60°.  In  the  plant  given 
and  those  similar  to  it,  however,  the  common 
FIG.  435.  channel  for  the  roller  mills  had  to  be  made  hori- 

zontal, and  therefore  it  contains  a  worm  D  for  the 
discharge  of  heavy  refuse.  The  necessity  of  grouping  the  sifters  for 
general  ventilation  in  a  similar  manner  required  a  worm  E.  The  ventila- 
tion worms  differ  from  the  ordinary  ones  in  that  their  chamber  is  made 
considerably  higher  (the  area  of  the  cross  section  is  lJ-2  times  as  large), 
to  allow  the  air  free  passage. 

In  this  plant  we  see  that  the  air  trunks  N  from  the  stone  mills  run 
directly  to  the  fan,  passing  the  filter  by,  as  the  millstones  have  their 
filters  in  the  chamber  of  the  casing. 

The  heavy  offals  and  flour  collected  by  the  worms  descend  along  the 
spouts  F  (from  the  worm  of  the  sifters)  and  G  (from  the  worm  for  the 
rolls)  to  the  nearest  elevators  corresponding  to.  the  quality  of  offals,  re- 
turning in  this  wise  to  the  stock  ;  the  light  dust  and  offals,  on  the  other 
hand,  pass  to  the  filter,  where  they  collect  in  the  worm  for  discharge. 

In  the  plant  we  are  examining  there  are  shown  two  variations  of 
exhaust  for  rolls  :  one  variation,  with  a  bottom  worm  with  ventilation  of 
the  spouts  H,  connected  with  the  ventilated  worm  D  by  the  air  trunk  /, 


CJHAP.  VIlJ 


FLOUR  MILLING 


441 


is  the  type  accepted  by  Seek  ;   the  other  the  one  most  generally  used, 
with  a  top  collecting  worm  D.  outlined  in  dots  under  the  ceiling  (Fig.  434). 


FIG.  436. 

The  comparative  merits  and  defects  of  these  two  variations  have  already 
been  spoken  of. 


442  FLOUR   MILLING  [CHAP,  vn 

Two  common  air  trunks,  L  from  the  worm  of  the  rolls  and  M  from  the 
worm  belonging  to  the  sifters,  convey  the  dusty  air  to  the  filter,  where 
it  deposits  the  dust  and  is  discharged  by  the  fan  through  the  trunk  B 
leading  outside  the  building. 

The  meal  dust  and  light  refuse  discharged  by  the  filters  descend  into 
the  bin  Q  and  a  worm  carries  them  out  to  the  spout  R,  where  they 
are  admixed  to  the  product  going  to  the  fifth  break.  The  spout  R  can 
also  deliver  the  filtered  product  to  the  centrifugal  or  directly  into  the  sack. 
In  any  case  this  spout  must  have  valves  p-p  (Fig.  435),  which  are  opened 
by  the  pressure  of  the  dust  discharged  and  prevent  the  back  draught  of 
air  into  the  niters,  otherwise  the  action  of  the  filters  would  be  weakened. 

Fig.  436  illustrates  the  exhaust  plant  of  a  wheat  mill.  In  com- 
parison with  the  preceding  one  there  is  an  extra  set  of  purifiers  here,  for 
which  a  pressure  filter  is  installed.  From  the  purifiers  the  dusty  air  is 
driven  by  their  fans  to  the  collecting  worm,  whence  it  passes  to  the  filter. 
The  sifters  and  roller  mills  are  exhausted  by  the  fan  operating  for  the 
suction  filter. 

3.  Calculation  for  an  Exhaust  Plant 

To  calculate  the  correct  size  of  an  exhaust  plant  it  is  necessary  to 
know  :  (1)  the  quantity  of  air  required  to  remove  the  dust  and  warm 
air  from  each  machine  ;  (2)  the  area  of  the  filtering  cloth. 

The  Area  of  the  Filtering  Cloth. — It  is  more  convenient  to  begin  by 
determining  the  necessary  area  of  filtering  cloth,  from  which  we  shall  pass  to 
the  calculation  of  the  volume  of  air  required  for  the  given  working  effect. 

Area  of  Filtering  Surface  for  Machines  of  the  Grain-cleaning  Depart- 
ment.— 

TABLE   XLIII 

CAPACITY  125  SACKS  PER  DAY  (24  HOURS) 


NAME  OP  MACHINE. 


Area  of  Filtering 

Cloth  in  Square 

Metres. 


Scales     ........ 

Separator  with  one  sieve  ..... 

Separator  of  the  zigzag  type 

Trieurs  (cylinders)     .          .          .          .          . 

Horizontal  emery  scourer.          .... 

Vertical  emery  (plate)  scourer    .          .          .          . 

Brush  machine,  horizontal          .          .        _^ --     .. 
,,  ,,         vertical    .          .       _.:.,  -~ 

,,  „         compound  vertical  *  .          .          . 

Combined  scouring  machine  of  the  Zolotukhin  type 


20-25 
25-30 
30-35 
12-15 
30-35 
30-35 
20-25 
20-25 
20-25 
40-45 


1  See  Fig.  95,  p.  103. 


CHAP,  vii]  FLOUR    MILLING  443 

As  regards  the  definition  of  the  area  of  the  filtering  cloth,  there  is  no 
possibility  of  any  theoretical  reckoning.  One  is  obliged  to  make  use  of 
the  practical  data  of  the  best  foreign  and  Russian  plants  of  to-day,  which 
we  shall  append.  These  data  refer  to  the  filtering  woollen  tissue  "  mal- 
ton  "  (German  cloth)  or  to  a  Russian  cloth  of  corresponding  density. 

The  less  limits  of  areas  refer  to  the  drier,  and  the  larger  limits  to  the 
damper  grain. 

Practice  has  proved  that  with  the  increase  of  capacity  of  the  machine, 
the  filtering  area  increases  in  proportion,  but  later  diminishes  by  10  to 
15  per  cent.  For  instance,  if  the  capacity  of  a  zigzag  separator  is  375 
sacks,  the  filtering  area  for  it  will  be  : 

3(3-0-3-5) -10-3  (31°0^>5)=2-7(3'0-3-5), 

i.e.  not  90-105  square  metres,  but  10  per  cent.  less. 

The  Area  of  Filtering  Surface  for  Machines  of  the  Milling  Department. — 
The  area  of  filtering  surface  for  machines  of  the  milling  department  is 
likewise  defined  from  experimental  data,  which  are  expressed  in  the  fol- 
lowing figures  : 

To  1  metre  of  length  of  a  pair  of  rolls  for 

wheat  .          .  .          .          .      1-25-1-75  sq.  mts. 

To  1  metre  of  length  of  a  pair  of  rolls  for  rye       2-5-3-0      „     ,, 
For  a  stone  mill  with  stones  1  metre  in  diam. 

(wheat  grinding)  .        -.          ."        .          .      1-35-2-0      .,     ,, 
For  a  stone  mill  with  stones  1  metre  in  diam. 

(rye  grinding)        .          .          .          .          .        3-0-3-5      ,,     ,, 

For  sifting  machines  50  per  cent,  of  the  filtering  area  necessary  for 
all  reduction  machines  is  required. 

For  purifying  machines  125  sacks  per  day  : 

(a)  Gravity  purifier  "  Groupe  "     .          .          .     10-15  sq.  mts. 
(6)  "  Double  Pur.  "  of  Haggenmacher  and  Voll  25-30    „     „ 

(c)  "  Salgir  "  of  Dobrovy  and  Nabholtz          .     35-40    ,,     „ 

(d)  Sieve  purifier  of  the  "  Reform  "  type        .     35-40    ,,     „ 

The  quantity  of  air  is  more  conveniently  defined  to  1  square  metre  of 
filtering  area.  Here  practice  has  also  established  definite  data.  7-8 
cubic  metres  of  air  are  required  for  1  square  metre  of  filtering  surface. 

To  obtain  a  draught  of  exhaust  air  there  are  set,  as  we  have  seen, 
fans  or  separate  fans  for  machines  having  no  fans  of  their  own.  The 
pressures  of  the  fans  within  the  machines  (scouring  machines,  separa- 
tors, purifiers,  &c.),  or  without,  are  generally  not  great,  namely,  from 
40  to  120  mm.  of  the  water  column. 


444  FLOUR   MILLING  [CHAP,  vn 

We  must  regard  the  capacity  of  fans  given  in  Table  XLIV  as  the 
normal,  which  should  serve  as  a  proving  capacity  for  the  catalogue  data 
of  different  firms. 

TABLE   XLIV 
CAPACITY  or  FANS 


Diameter  of 
Wings, 
mm. 

Diameter  of 
the  suction 
holes, 
mm. 

Number  of  Revolutions 
per  1  Minute. 

Volume  of  Air 
Delivered  per  1 
Minute  in  Cubic 
Metres. 

Number  of  Horse  - 
Tower  Required. 

300 

160 

2100-2500 

25-30 

0-3-0-5 

375 

200 

1650-2000 

38-45 

0-5-0-75 

450 

250 

1400-1650 

50-60 

0-75-1-10 

600 

330 

1050-1250 

100-125 

1-5-2-0 

800 

440 

800-950 

220-250 

3-5-4-0 

1000 

550 

650-750 

350-400 

5-0-6-0 

1200 

660 

500-600 

500-600 

7-5-9-0 

Once  we  have  the  above-mentioned  data,  the  calculation  of  the  details 
for  any  exhaust  system  may  be  undertaken. 

For  example,  we  shall  reckon  out  the  plant  of  the  rye  mill  (Figs.  433 
and  434)  with  high  grinding  we  have  examined,  which  has  three  double 
roller  mills  with  rolls  800,  700,  and  600  mm.  long,  two  stone  mills  with 
stones  1300  mm.  in  diameter,  two  sifters,  and  one  reel  separator. 

Suppose  we  are  grinding  rather  damp  rye.  Then  a  larger  filtering 
surface  according  to  our  data  has  to  be  employed. 

Three  mills  require  : 

3  sq.  mts.  x  4 -2  =  12 -6  sq.  mts.  of  filters. 

Two  stone  mills  : 

3x2-6  =  7-8  sq.  mts. 

Consequently,  the  reduction  machines  must  have  20-4  sq.  mts. 
The  bolting  machines,  50  per  cent,  of  20-4  sq.  mts.  =  10-2  sq.  mts. 
The  total  is  30-6  sq.  mts.     The  quantity  of  air  necessary  for  venti- 
lation is  : 

30-6x8=244-8  cubic  metres, 

which  will  need  a  fan  with  wings  800  mm.  in  diameter  running  at  the 
rate  of  960  revolutions  per  minute. 

If  we  decide  upon  a  common  pressure  tubular  filter  for  all  machines, 
millstones  included,  then  the  diameter  of  the  tubes  being  90  mm.  (3j 
inches),  a  filter  with  56  or  60  tubes  2  metres  long  will  be  required. 

The  section  of  the  air  trunks  may  be  calculated  according  to  the  con- 
sumption of  air. 


CHAP,  vii]  FLOUR    MILLING  445 

The  general  air  trunk  L  for  the  roller  mills  must  give  passage  to  12-6  x  8 

=  100-8  cubic  metres  of  air  per  minute,  and  cubic  metres  per 

second.  Accepting  the  velocity  of  passage  of  the  air  from  the  ven- 
tilated machines  down  the  air  trunks  (Figs.  433  and  434)  /,  K,  and  N 
on  the  average  to  be  1-5  metres  per  second  and  15-25  metres  per  second 
down  the  collecting  spouts  L,  M,  and  b,  it  is  easy  to  calculate  the  dimen- 
sions of  the  transverse  section  of  the  air-conducting  trunks.  As  regards 
the  shape  of  section  of  the  trunks,  round  is  best,  as  it  offers  less  resistance 
to  the  motion  of  air.  But  trunks  of  rectangular  section  being  more  easily 
made,  these  may  be  used  for  a  short  travel. 


IV 

TRANSPORTATION  OF  STOCK 
1.  Spouts  and  Elevators 

Modern  industrial  mills  are  almost  exclusively  automatic  ;  the  whole 
travel  of  the  stock,  beginning  with  transportation  of  the  stock  to  the 
storing  bin  and  ending  with  the  delivery  of  flour,  takes  place  without  any 
expenditure  of  manual  work.  Therefore  the  arrangement  and  a* correct 
calculation  of  dimensions  of  the  transportation  devices  is  of  vital  import- 
ance. The  transportation  devices  must  be  so  constructed  as  to  answer 
the  given  capacity  (without  any  reserve  for  the  enlargement  of  the  mill) 
and  consume  the  least  amount  of  power.  That  will  be  the  basis  of  our 
estimation  of  the  transport  constructions,  which  we  are  about  to  examine 
in  this  part. 

All  the  modes  of  transportation  may  be  divided  into  two  groups  : 

1.  Transposition  of  the  stock* from  one  height  to  another  down  from 
the  top  or  the  reverse. 

2.  Transposition  of  the  stock  within  the  bounds  of  one  horizontal  plane. 
Delivery  of  the  Stock  Downwards :  Spouts. — For  the  transmission  of  the 

product  in  a  downward  direction  there  are  drain  pipes,  automatic  dis- 
chargers, or,  as  they  are  more  often  called,  spouts.  The  spouts  generally 
carry  the  stock  from  the  machine  to  the  elevator  or  the  reverse,  from 
machine  to  machine,  and,  lastly,  from  the  binjbo  the  sacks  for  packing  the 
finished  product — the  flour.  In  the  first  two  cases  the  spouts  have  always 
to  be  set  aslant,  and  in  the  third  possibility  and  convenience  allow  the 
position  of  the  spouts  to  be  vertical,  because -the  greater  the  speed  of  the 
flour  flowing  out  of  the  bin,  the  faster  and  more  compact  will  be  the  packing. 


446 


FLOUR   MILLING 


[CHA£.  vii 


It  is  easy  to  deduce  the  condition  under  which  the  motion  of  the 
stock  over  an  inclined  plane  is  possible.  If  we  have  a  spout  (Fig.  437) 
inclined  to  the  horizon  at  an  angle  a,  and  suppose  the  weight  Q  on  a  unit 
of  area  of  the  spout  to  be  equal  to  6r,  and  the  coefficient  of  friction  of  the 
stock  upon  the  surface  of  the  spout  /,  the  motion  of  the  product  is  possible 
under  the  condition  that  : 

T-Nf>6 (1). 

And  since 

T —G  sin  a  and  N=G  cos  a, 

by  substituting  the  values  T  and  N  into  (1),  we  obtain  : 

f<Tga. 
In  other  terms,  the  motion  of  the  stock  in  the  spout  is  possible  only 


B 


FIG.  437. 


FIG.  438. 


in  case  the  coefficient  of  friction  of  the  product  upon  the  surface  of  the 
spout  is  less  than  the  cotangent  of  the  angle  of  incline  of  the  spout. 

For  wood  spouts  practice  has  established  the  following  least  values 
of  the  angle  a  for  different  products  : 

For  grain   .......  25-30  degrees 

„  high  break                                  T                    .  40-50  „ 

„  low  break     ......  50-60  „ 

„  large  middlings      .....  45-50  „ 

„  medium  middlings          .                    .          .  50-55  „ 

„   dunst 55-60  „ 

„   bran 60-65 

„  flour  and  dust        .....  70-80  „ 

It  will  be  well  to  give  the  limit  values  of  the  greatest  horizontal  trans- 
mission of  the  stock  when  it  is  delivered  by  the  spout.  If  from  the  point 
A  (Fig.  438)  the  product  passes  to  the  point  B,  the  quantity  sought  for  a 
is  expressed  in  accordance  with  h  thus  : 

a=h  Ctga, 


CHAP.    VII] 


FLOUR    MILLING 


447 


If  h  =  l  (metre,  yard,  &c.)  we  obtain  a  for  various  products. 
If  a =26— 30— 35— 40— 45— 50— 55—60— -65— 70— 75  degrees, 
then  a  will  correspondingly  be  equal  to  : 

a=2-l5— 1-73— 1-19— 1-00— 0-84— 0-70— 0-57— 0-47— 0-36— 0-27  mts. 

Hence  it  is  easy  to  define  the  value  of  a  for  different  h,  since  a  increases 
or  decreases  in  proportion  to  h. 

As  to  the  constructive  side  of  the  spouts,  they  are  either  rectangular 
or  round  in  their  cross  section.  The  spouts  with  a  round  section  are 
made  of  iron  or  zinc  sheet  iron. 

Spouts  with  a  rectangular  section  are  generally  made  of  pine  tree 
planks  f  to  1  inch  thick.  The  planks  are  joined  by  overlapping,  i.e.  by 
simply  laying  them  on  and  nailing  or  coupling  them  with  wood  screws  ; 
or  by  covering  as  shown  on  Fig.  439,  or  by  grooving  and  tonguing, 
Fig.  440.  The  last  joint  is  the  best,  and  the  grooves  may  run  in  one 


FIG.  439. 


FIG.  440. 


FIG.  441. 


direction  a  and  at  right  angles  b  :  the  covering  comes  next,  and  the  worst, 
the  overlapping  joint,  should  be  avoided,  as  it  is  not  hermetically  closed 
against  air,  which  reduces  the  efficiency  of  the  ventilation  plant. 

To  lessen  the  friction,  the  lower  part  of  the  spout  over  which  the  stock 
travels  is  lined  with  sheet  iron. 

Sometimes  the  ^oduct  has  to  be  transferred  from  one  spout  to  another. 
In  such  cases  there  is  made  a  transfer  valve,  as  illustrated  on  Fig.  441. 
When  the  valve  lies  in  position  1  the  products  out  of  spouts  A  and  B 
flow  into  one  common  spout  Bl3  if  its  position  is  2  ;  into  spout  A^  if  3  ; 
out  of  B  the  product  runs  into  A 15  and  out  of  A  into  B±. 

The  vertical  spouts  for  the  flour  packing  by  hand  end  in  bosses  on 
which  sacks  are  fitted.  Fig.  442  shows  various  constructions  of  cast-iron 
bosses.  Nos.  1,  2,  3,  4,  and  5  have  a  gate  valve  to  stop  the  flow,  and 
No.  6  has  a  valve  A  which  is  turned  by  means  of  a  handle  B.  No.  7 
illustrates  this  valve  in  a  half -opened  position. 

The  diameters  of  the  bosses  are  250  to  350  mm. 


448 


FLOUR    MILLING 


[CHAP,  vn 


The  sack  is  fastened  to  the  boss  by  a  strap  with  a  French  clasp  A 
(Fig.  443).  The  strap  is  suspended  to  the  spout  by  means  of  "  ears  "  a. 
When  the  empty  sack  is  fitted  on  the  boss,  the  clasp  is  coupled  and  the 


Jfe  1 


Jfe  3 


JVs  6 


FIG.  442. 

handle  c  turned  as  indicated  by  the  arrow  6,  owing  to  which  the  strap 
tightly  fastens  the  sack  to  the  boss. 

Transmission  of  the  Product  Upivards  :  Elevators. — The  upward  trans- 
mission of  .the  stock  in  the  mill  is  generally  effected  with  the  aid  of  ele- 
vators or  automatic  lifts,  which  consist  of  an  endless  belt  with  boxes 

(cups,  buckets)  attached  to  it  and  running 
over  pulleys,  one  of  which  is  set  below, 
in  the  boot  of  the  elevator,  and  the 
other  at  the  top — in  its  head.  On  the 
same  shaft  with  the  top  pulley  is  set  the 
driving  pulley  to  wh&h  the  belt  from  the 
shafting  runs.  The  belt  with  the  buckets 
is  enclosed  in  a  timber  or  iron  case  or 
leg  to  avoid  any  loss  or  scattering  of 
the  product  delivered.  On  Fig.  444  a 
wood  elevator  is  shown. 
The  elevators  are  always  set  vertically,  and  only  very  rarely,  in  case 
of  extreme  need,  an  incline  is  allowed  of  not  more  than  J,  because  other- 
wise the  sag  of  the  belt  on  the  right  side  compels  it  to  slide  over  the  left- 
hand  inner  wall  of  the  leg,  which  damages  the  belt  and  incurs  extra 
consumption  of  power,  and  the  sag  of  the  left  side  leads  to  the  cups 


FIG.  443. 


CHAP.   VII] 


FLOUR   MILLING 


449 


coming  in  contact  with  the  leg,  which  results  in  extra  work  of  friction 
and  in  the  cups  and  leg  being  damaged. 

The  timber  legs  of  the  elevators  should  be  built  in  the  same  manner 
as  the  spouts,  i.e.  by  tonguing  and  grooving.     Iron  legs  of  small  dimen- 


FIG.  444. 

sions  are  made  of  iron  plate  with  the  bend  of  the  grooves  down  the  seams, 
and  the  large  ones  are  joined  with  rivets. 

The  belts  are  generally  of  leather  or  plaited  of  camel-hair. 

The  cups  are  made  of  iron,  galvanised  sheet  iron,  tinplate,  or  black 
iron  plate.  According  to  the  manner  of  manufacture  there  are  stamped 
cups  with  a  bend  of  the  groove,  and  riveted  cups.  In  Russia 

2F 


450 


FLOUR   MILLING 


[CHAP,  vn 


there  are  used  cups  with  the  seams  joined  by  overlapping  with  bent 
grooves.  In  Western  Europe  and  in  America  these  cups  are  being  sup- 
planted by  those  bossed  of  a  whole  piece,  these  being  lighter.  The 

riveted  cups  are  used  for   heavy 

work,  when  they  have  to  be  of  a 

large  size. 

Every  cup  is  characterised  by 

three   measurements    (Fig.    445)  : 


B    - 


FIG.  445. 


width  B,  projection  A,  and  height 
H.  In  the  back  wall  of  the 
cup  there  are  made  holes  for 
fastening  them  on  to  the  belt  with 
special  bolts. 

Fig.  446  illustrates  six  different  types  of  cups.  No.  1  has  a  riveted 
bottom,  Nos.  2,  3,  4,  and  5  of  medium  size  are  bossed,  and  No.  6,  a  cup 
for  large  capacities,  is  manufactured  of  comparatively  thick  iron,  up  to 
2-2 1  mm.,  whereas  the  ordinary  cups  are  made  of  tin  plate  or  iron  1-1 J 
inch  thick.  Boxes  of  thin  tin  plate,  as  No.  3,  have  a  cover  plate  a  for 

4 


FIG.  446. 


FIG.  447, 


strength  and  better  resistance  to  wear.     On  Fig.  447  is  shown  the  best 
shape  for  bolts  with  a  flat  head. 

As  regards  the  dimensions  of  the  cups,  for  mill  elevators  they  may 
be  represented  by  the  following  figures  (Schmidt's  works  in  Wurzen, 
Germany)  : 


CHAP.    VII 


FLOUR   MILLING 


451 


TABLE  XLV 


Nos.  of  Cups. 

!    (z; 

d 

o 

£ 

SO 

1 

I 

in 
0 
fe 

130 

'     co 

6 

% 

140 

r^ 

d 
fc 

150 

00 

0 

% 

**     s  Is 

o'          6     :     d 
fc          fc          Sz? 

<*• 

d 
H5 

B—  Width,  mm.          .   !  90 

100 

110 

120 

160 

170 

180 

190 

200 

A  —  Projection,  mm.  .       85 

90 

100 

105 

115 

120 

125 

130 

135 

140 

145 

150 

H—  Height,  mm.         .      65 

75 

80 

90 

97 

105 

115 

120 

130 

135 

145 

150 

F-Capacity  (f   full)V0.20 
litres.         .        .j 

0-27 

0-35 

0'45 

0-55 

0-67 

0'80 

1-00 

1-20 

1-40 

1-65 

1-80 

Another  manufacturer,  Dietz  in  Leipzig,  gives  cups  with  a  less  variety 
of  projections  and  heights,  but  with  such  a  matching  of  these  sizes,  that 
the  working  capacity  of  the  cup,  f  full,  is  greater  than  Schmidt's. 


TABLE    XLVI 


Nos.  of  Cups. 

d 
fe 

c4 

d 

£ 

eo 
I 

Tjl 

d 
fc 

vd 

1 

!  » 
1 

J>^   I   00 

4  :-l 

1 

0 

6 
|^ 

T-4 

d 
* 

oi 

o" 
& 

B   .    .    .   „. 

90 

100 

110 

120 

130 

140 

150  160 

170 

180 

190 

200 

A   ,'...*  J.y/v  -.  "..  •; 

80   95 

100 

110 

115  115 

115  j  115  ;  115 

115 

120 

120 

H  V:  *   . 

90   95 

95 

110 

115 

115 

115  130  ^  130 

130 

135 

140 

V 

0-72  0-95 

1-10 

1-20 

1-50 

1-61 

1-72  1-84  -T95 

'''••   \'  •   ; 

2-00 

2-28 

2-40 

The  filling  V  of  cups  of  the  mentioned  constructions  must  not  exceed 
f  of  their  capacity,  otherwise,  as  has  been  proved  by  experience,  the  whole 
of  the  product  will  not  be  thrown  out  into  the  discharge  spout. 

The  diameters  of  the  belt-pulleys,  the  number  of  cups  to  one  metre  of 
length,  and  the  capacity  per  hour  in  litres,  are  shown  in  the  appended 
table. 

TABLE    XLVII 


Nos.  of  Cups. 

No.  1. 

Nos.  2-3. 

Nofc.  4-6.           Nos.  7-8. 

Nos.  9-10. 

Nos.  11-12. 

• 

Diameter  of  belt  pulleys 

Number  of  cups  to  1  ) 
metre       .         .     •   »  f 

Capacity  per  hour  in  ) 
litres        .         .        .  f 

400-500 
12 

12,500 

500-600 
12-10 

15,000-10,000 

500-600          600-700 
10-8                  8-6 

20,000-25,000^30,000-40,000 

700 
6-5 

45,000-50,000 

700-800 
5-4 

55,000-60,000 

452 


FLOUR   MILLING 


[CHAP,  vn 


To  bring  the  constructive  description  of  elevators  to  a  close  we  -must 
give  an  idea  as  to  the  arrangement  of  cups,  cleaning  of  elevator  legs, 
and  the  constructions  of  the  boots  and  heads  of  the  elevators. 

The  preceding  table  shows  us  that  the  cups 
are  generally  set  on  the  belt  in  such  a  manner  as 
to  leave  a  space  of  10-65  mm.  between  them. 
But  of  late  they  are  aiming  at  a  total  abolition 
of  the  distance  between  the  cups,  as  is  shown  on 
Fig.  448,  in  order  to  increase  the  capacity  of 
elevators  without  increasing  the  dimensions  of 
the  cups.  In  such  cases  the  top  part  a  of  the 

M         s^^s  cups  is  made  so  much  wider  that  the  bottom  of 

the  cup  above  may  enter  into  the  cup  below,  in 
which  sometimes  a  notch  of  the  top  line  a  is  made. 
The  construction  of  compact  arrangement  of 
cups  just  examined  imparts  greater  rigidity  to  the 
belt,  which  demands  a  larger  consumption  of  power 
to  overcome  the  injurious  resistances  ;  but  in  its 
final  result  the  useful  work  of  such  an  elevator  is 
greater  than  with  the  cups  set  apart. 
For  freeing  the  elevator   legs   of   dust   there    are  brushes  b,  which 
touching  the  walls  of  the  spout  with  their  edges  sweep  the  dust  off. 


a 


FIG.  448. 


FIG.  449. 


FIG.  450. 


The  essential  parts  of  an  elevator  are  its  boot  and  head,  in  which  the 
belt-pulleys  are  set.  The  simplest  kind  of  a  wooden  boot  and  head  is 
given  in  Figs.  449  and  450.  The  boot  is  a  plain  wood  box  with  a  feed 


CHAP,  vn] 


FLOUR   MILLING 


453 


spout  B.  The  bearings  for  one,  or  if  the  elevator  is  double,  for  two 
pulleys,  are  set  on  cross  bars,  fastened  to  the  box  with  bolts.  For  inspec- 
tion of  the  chamber  in  the  boot  in  case  of  a  choke  there  is  a  door  A. 
The  head  is  also  a  box  with  a  discharge  tube  Slt  a  door  for  inspection  of 


FIG.  451. 


FIG.  452. 


FIG.  453. 


the  belt-pulley,  and  a  hatch  C  for  controlling  the  discharge  of  the  product 
by  the  cups. 

Among  the  defects  of  this  construction  must  be  mentioned  the  im- 
possibility of  regulating  the  tension  of  the  belt  without  lacing  it  over. 

In  Figs.  451  and  452  may  be  seen  the   simplest  construction  of  an 


FIG.  454. 


FIG.  455. 


American  wooden  head  and  boot  without  the  possibility  of  adjusting  the 
tension  of  the  belt,  and  in  Fig.  453  we  have  a  wooden  boot  with  adjustable 
bearings  which  may  be  lowered  with  the  aid  of  screws  a  with  hand-wheels. 
The  metal  constructions  of  boots  of  the  American  type  are  shown 
in  Figs.  454  and  455.  The  first  is  iron  and  riveted,  the  second  has  a 


454 


FLOUR   MILLING 


[CHAP,  vn 


cast-iron  or  ingot  steel  frame.     The  bearings  here  are  adjustable,  and  the 
regulation  of  tension  of  the  belt  is  easy. 

In  Figs.  456  and  457  we  have  the  perspective  view  of  a  wood  and 
an  iron  elevator  of  the  Amme,  Giesecke  and  Konegen  system  very  ration- 
ally constructed.  The  bearings  of  the  boots  are  adjustable,  the  door  A 
allows  of  inspecting  the  lower  belt-pulley,  and  the  hatch  B  is  made  for 
cleaning  the  boot  in  case  it  is  blocked  up  with  product.  The  lower  part  C 

of  the  left-hand  side  leg 
in  the  iron  elevator  is  built 
up  and  has  a  door  for 
inspection.  The  heads  of 
the  wood  and  the  iron  ele- 
vator can  be  easily  taken 
off  and  dismantled. 

Useful  Work  of  the  El- 
evators.— The  efficiency  of 
an  elevator  depends  on  the 
following  circumstances  : 

1.  Shape   of    the  cup, 
which  determines  its  cap- 
acity. 

2.  Capability    of    the 
cup  of  retaining  the  pro- 
duct   on    the    way   from 
charging  to  emptying. 

3.  Capability    of    the 
cup   of   emptying  at   the 
spot   given.      The  shapes 
of  cups  we  examined  de- 


FIG.  456. 


FIG.  457. 


termine  their  capacity. 
For  the  definition  of  the  ability  to  retain  the  stock  during  the 
travel  and  to  empty  the  cups  the  following  line  of  reasoning  is 
suggested. 

Supposing  on  the  belt-pulley  S  (Fig.  458)  of  the  elevator  boot  we  have 
a  cup  U  fastened  to  the  belt  E  running  upwards. 

The  middle  of  the  projection  of  the  cup  K  lies  at  a  distance  r  from  the 
axis.  0  of  the  belt-pulley,  OK  forming  an  angle  <j>  with  the  vertical ;  the 
angular  velocity  of  rotation  of  the  box  is  «,  the  weight  of  the  particle  of 
product  at  K  mg,  and  the  centrifugal  force  of  rotation  of  this  particle 


CHAP.    VII] 


FLOUR   MILLING 


455 


Then  the  resultant  T  of  the  forces  mg  and  mr w2  will  be  expressed  by 
the  diagonal  of  the  parallelogram,  and  its  direction  will  be  determined 

by  the  angle  a  : 

BD    AB+AD 
Tga=DK~ 


DK 


But  since 
we  obtain  : 


cos 


rt»2  sin  <f> 

Further,  we  shall  define  the  point  L  intersection  of  the  direction  of 
the  resultant  and  the  vertical  axis  of  the  elevator  : 


h  =LF  -OF  =r  sin  <f>  Tga  -r  cos  <£  =9+rco*°s  ^  _ 


r  cog 


whence  we  obtain  :  Ti  =  ^  i.e.  h  is  a  constant  quantity.     In  other  terms, 
the  position  of  the  intersection  point  of  the  resultant  T  with  the  vertical 


M 


Fio.  458. 


axis  of  the  elevator  depends  only  on  the  angular  velocity  of  rotation  of 
the  belt-pulley.     The  quantity  h  may  be  defined  in  accordance  with  the 

number  of  revolutions  n,  by  substituting  w~  -TTT,  and  after  some  altera- 
tion we  obtain  : 

J.          894'56  /0\ 

h  =  — r 2  •     •  .'•  v    • \*>' 


If  the  cup  A  (Fig.  459)  were  to  contain  a  fluid,  when  in  motion  the 
level  of  this  fluid  would  be  defined  by  a  cylindric  surface  ba,  where  the 


456 


tfLOUR   MILLING 


[CHAP,  vil 


point  b  is  the  highest  position  of  the  route  over  the  circumference  of  the 
cup.     But  for  dry  substances  the  surface  ba  changes  to  ba1  so  that  its 

angle  of  oscillation  ft  (the  angle  of 
the  tangents  at  b)  forms  approxi- 
mately the  angle  of  natural  deflec- 
tion of  the  product. 

The  data  defining  the  favourable 
conditions  of  delivery  of  the  stock, 
we  can  deduce  starting  with  the 
supposition  that  the  trajectory  of 
motion  of  the  product  must  be  LS 
and  not  LS1  for  the  product  to 
drop  into  the  outlet  spout  A,  and 
not  into  the  leg  B  of  the  elevator 
(Fig.  460). 

At  the  moment  of  ejection  from  the  cup  the  product  has  the  velocity 
of  motion  of  the  belt  v.     Its  horizontal  resultant  is 


FIG.  460. 


"1 


f 


=V  COS  a 


(3), 


and  the  motive  force  in  the  vertical  direction  (gravity)  mg=m  ^-, 
whence 


(4). 


Having  integrated  these  equations  and  excluded  t  from  them,  we 
obtain  an  equation  of  the  curve,  denning  the  law  of  motion  of  the 
product. 

For  the  calculation  of  elevator  capacities  Professor  Fischer  gives  the 
following  empiric  formulae. 

Supposing  we  have  : 

D — diameter  of  the  belt  pulley. 

n — number  of  revolutions  per  minute. 

A — projection  of  the  cup. 

B — breadth  of  the  cup. 

F — distance  of  the  summit  of  the  rib  /  to  the  horizontal  plane 

OJI. 

iv — distance  between  the  walls  of  the  casing. 
L — capacity  of  the  elevator  in  kilogrammetre-seconds. 
M — capacity  per  second  in  litres. 


CHAP,  vn]  FLOUR   MILLING  457 

All  the  lineal  quantities  here,  D,  A,  J3,  F,  andw  are  given  in  metres. 

For  the  quantities  mentioned,  supposing  the  highest  limit  for  r=—=h 

(Fig.  458),  we  have  : 

36-8 
*-'-  jp 

A^fl-llD, 


For  the  definition  of  the  number  N  of  horse-power  required  by  the 
elevator,  F.  Baumgartner  offers  the  following  formula  :  l 


where  L  is  the  capacity  of  the  elevator  per  hour  in  hectolitres,  H  the 
height  of  elevation  in  metres,  and  y  the  coefficient  equal  :  for  grain  to 
0*75,  for  break  chop  0-5,  for  bran  0-35,  and  for  middlings  0-30. 

If  we  accept  the  denominations  V  for  the  bulk  of  product  lifted  in 
litres,  ri  for  its  specific  gravity,  and  H  for  the  height  of  elevation,  then 
the  number  N  of  horse-power  for  an  elevator  according  to  the  data  of 
the  Nagel  and  Kamp  works  (Hamburg)  will  be  : 

N  =  (l-33-2)VrjH. 
Luther's  works  (Brunswick)  give  : 

#=--1-66  VfjH. 

And,  finally,  Professor  Fischer,  taking  for  granted  that  the  elevator 
is  carefully  looked  after,  suggests  : 


For  the  definition  of  the  working  (f  full)  capacity  /  of  the  cup  in  litres 
Baumgartner  suggests  the  following  formula  : 


T=- 


Q 


3600  yt*' 

Where  p  is  the  same  coefficient,  v  the  velocity  of  motion  of  the  belt  per 
second  in  metres,  z  the  number  of  cups  to  1  metre  of  the  belt. 

1  F.  Baumgartner  does  not  mention  the  origin  of  his  formulae. 


458  FLOUR   MILLING  [CHAP,  vtt 

The  velocities  of  motion  of  the  cups  for  different  products  are  different. 

Velocity  for  grain   ....     2-3  mts.  per  second. 
Velocity  for  middlings     .          .          .      1-5-2-0  mts.  per  second. 
Velocity  for  flour    ....      1-25-1-5  mts.  per  second. 

The  diameters  of  the  belt-pulleys  for  elevators  are  300-700  mm.  The 
number  of  revolutions  of  the  belt -pulleys  fluctuates  between  40  and  90, 
depending  on  their  diameters  and  the  given  velocity  of  the  belt. 

Before  closing  the  part  treating  of  elevator  transport  we  must  give 
the  bulk  weights  of  grain  and  the  intermediate  products.  Below  is  given 
a  table  of  weights  in  kilograms. 

WEIGHT  OF  1  LITRE  IN  KILOGRAMS 

Wheat       ....     0-7-0-86  Wheat  middlings  0-55-0-65 

Rye 0-6-0-8  Large  wheat  bran  0-29-0-35 

Barley      .      .      .      .0-6-0-78  Fine  wheat  bran  .  0-32-0-60 

Oats 0-43-0-54  Large  rye  bran     .  0-37-0-44 

Wheat  semolina .      .     0-35-0-43  Wheat  flour     .      .  0-41-0-80 

Rye  semolina      .      .     0-50-0-55  Rye  flour  .      .      .  0-57-0-60 

2.  Horizontal  Transport 

Archimedean  Screw. — The  Archimedean  screw,  worm,  or  conveyor 
is  one  of  the  oldest  mechanisms  of  automatic  transportation.  This 
mechanism  is  a  rotating  helical  surface,  encased  in  a  box,  which  is  the 
route  of  transport.  The  transporting  action  of  the  screw  is  based  on  the 
fact  that  dry  substances  travel  down  the  length  of  the  box  or  the  axis 
when  the  angle  of  the  helical  surface  is  less  than  the  angle  90  —  </>,  where 
<t>  is  the  angle  of  friction  of  the  product  against  the  surface  of  the  screw. 
One  turn  of  the  screw  brings  the  product  forward  (theoretically)  by  the 
size  of  the  thread,  which  is  expressed  by  the  formula  nDtga,  where  D  is 
the  diameter  of  the  screw,  and  a  its  angle. 

The  working  organ,  as  we  have  said,  is  the  helical  surface,  a  perspec- 
tive view  of  which  is  shown  on  Fig.  461,  No.  1.  This  surface  consists  of 
the  separate  sections  of  "feathers"  given  below  in  A.  The  diameter 
is  defined  and  these  sections  formed  in  the  following  manner. 

Supposing,  according  to  our  calculation,  we  need  a  worm  with  a  dia- 
meter D  and  a  thread  h.  We  have  to  define  d  the  diameter  of  the  opening 
of  the  feather.  The  length  of  circumference  of  the  d  sought  for  is  a 
helical  line  with  a  pitch  h.  The  angle  of  the  screw  is  a ;  consequently, 

h—ndtga,  whence  we  define  d= . 

n  .  tga 


CHAP.    VIl] 


FLOUR   MILLING 


450 


Having  defined  the  d,  iron  plate  or  zinc  tin  is  taken  of  which  the  sec- 
tions of  the  worm  are  prepared,  and  several  rounds  cut  out  with  the 
diameter  D-^-d—d^  where  d±  is  the  diameter  of  the  shaft,  with  concentric 
openings,  d  in  diameter.  Then  they  are  cut  and  in  the  ends  b  there  are 
holes  perforated  for  rivet  joints.  The  sections  distributed  along  the 
screw  are  joined  with  rivets. 

Besides  the  ordinary  worm  No.  1  (S  right-hand  thread,  and  S±  left- 
hand)  of  the  same  sections,  the  paddle  worm  No.  2  is  made  by  cutting 


FIG.  461. 

the  feather  down  its  radius  and  the  concentric  circle  in  four  or  five  places, 
and  the  parts  k  are  bent  at  an  angle  to  the  axis  of  the  worm.  In  this 
manner  an  enlargement  of  the  screw  thread  is  attained  and  a  more  ener- 
getic stirring  of  the  product.  These  worms  are  mostly  used  in  America. 

The  worms  Nos.  3  and  4  have  separate,  not  joined  to  each  other, 
sections  t.  These  sections  are  cast  of  malleable  cast  iron  and  screwed 
to  the  shaft  of  the  worm,  which  is  an  ordinary  gas-pipe. 

The  worm  No.  5  is  called  the  band  worm.  Its  arrangement  is  clear 
from  the  drawing  without  any  description.  It  is  used  for  the  transporta- 
tion of  light  product  in  purifiers,  &c. 


460 


FLOUR   MILLING 


[CHAP,  vii 


The  worms  Nos.  3  and  4  have  this  advantage  over  Nos.  1,  2,  and  5, 
that  the  direction  of  motion  of  the  product  may  be  altered  by 
turning  the  paddles  t  round  their  axis  by  90°.  Besides  that,  by 
turning  t  round  their  axes  to  a  larger  or  smaller  angle,  the  pitch  of 


FIG.  462. 

the  worm,  and  consequently  the  velocity  of  motion  of  the  product,  can 
be  altered. 

On  B  and  C  are  illustrated  the  boxes  or  tubes  of  the  worms  generally 
met  with  in  practice.  Both  the  boxes  are  of  timber,  and  the  first  has  a 
timber  bottom  lined  with  tin  r,  to  reduce  friction  of  the  product.  The 
bottom  of  the  working  space  in  the  second  worm  is  of  iron.  The 
constructions  of  the  bearings  are  sufficiently  clear  and  need  no 
description. 

A  whole  iron  box  of  a  worm  is  shown  on  Fig.  462.     The  most  charac- 


FIG.  463. 


FIG.  464. 


teristic  combination  of  transport  by  worms  is  the  transmission  of  product 
at  right  angles,  shown  on  Figs.  463  and  464.  In  the  first  case  it  is  done 
by  an  ordinary  bevel  gear  system,  and  in  the  second  we  have  a 
chain  gear. 

Turning  now  to  the  question  concerning  the  calculation  of  the  helical 
transportation,  we  must  say  that   its  theory  is  too  weak  and  confines 


CHAP,  vn]  FLOUR    MILLING  461 

itself  only  to  the  above  considerations  respecting  the  angle  of  the  worm 
surface.  All  the  data  of  calculation  are  worked  out  by  practice  and 
grouped  into  empiric  formulae  by  Professor  Fischer. 

The  diameter  D  of  the  worm  accepted  in  European  practice  is  100- 
500  mm.,  while  in  America  it  is  100  to  400-450  mm. 

The  thread  h  of  the  worm  in  accordance  with  D  : 


The  number  of  revolutions  n  per  minute  : 

45 


n= 


The  capacity  L  per  second  in  litres  is  : 


D  being  taken  in  metres. 

If  the  capacity  L  is  sought  for,  the  diameter  of  the  worm  D  may  be 
defined  from  the  preceding  formula  : 


The  distance  a  between  the  bearings  supporting  the  shaft  of  the  worm 
is  defined  according  to  the  formula  : 


The  consumption  of  work  in  horse-power  is  : 


where  I  is  the  length  of  the  worm  in  metres,  L  the  capacity  in  litres, 
y  the  weight  of  a  litre  in  kilograms,  and  /  the  practical  coefficient,  which 
has  a  numerical  value  of  from  1'35  to  1-8. 

F.  Baumgartner  gives  another  formula  of  capacity  per  hour  in  kilo- 
grams, namely  : 


where  D  is  the  diameter  of  the  worm  in  decimetres,  n  the  number 
of  revolutions  per  minute,  and  h  the  thread  of.  the  worm  in  deci- 
metres. 

As  in  most  cases,  Baumgartner  does  not  explain  the  origin  of  his 
formulae.  Fischer's  formulae  are  based  on  the  experimental  data  of  the 
works  of  Luther  and  of  Nagel  and  Kamp,  which  date  to  1890,  and  are 
consequently  obsolete  for  modern  types  of  constructions.  Baumgartner  's 
formulae,  on  the  other  hand,  in  no  respect  correspond  to  the  practical 
data  and  cannot  therefore  be  used. 


462  FLOUR    MILLING  [CHAP,  vn 

The  following  considerations  must  serve  as  the  correct  basis  on  which 
the  capacity  of  the  worm  is  calculated.  We  must  take  the  area  of  cross 
section  of  the  product  rilling  the  box  of  the  worm,  and  the  velocity  of 
motion  of  the  product,  which  depends  on  the  thread  of  the  worm  and  on 
the  coefficient  of  friction  of  the  product  against  the  worm.  This  velocity 
may  be  defined  only  practically.  By  introducing  a  practical  correcting 
coefficient  into  the  formula  of  the  quantity  of  product  running  in  a  unit 
of  time  through  the  given  cross  section,  we  obtain  the  capacity  of  the 
worm  Q  : 


Our  researches  have  proved  that  D  and  v  given  in  metres  n  is  expressed 
by  a  numerical  quantity  450. 
In  this  manner  for  Q  we  have  : 


Experimental  investigations  show  that  v  is  expressed  in  accordance 
with  the  thread  h  of  the  worm  and  its  number  of  revolutions  per 
minute,  thus  : 


.....    for  flour. 

v2  =  (0-40-0-43)/m     .          .          .          .  ,,  dunst. 

t;8  =  (0-50-0-54)&fl-     .          .          .          .  middlings. 

v4=(0-56-0-60)&w-     .          .          .          .          .       „  break. 
v5  =  (0-62-0-72)/m     ......  grain. 

For  the  existing  factory  dimensions  of  worms  with  their  h  = 
250  mm.  these  velocities  per  minute  will  be  expressed  in  round  numbers  : 
t>i=4,  v.2=5,  v3  =  6,  v4  =  7,  and  v5  —  S.  Consequently,  the  capacity  Q  in 
its  final  shape  per  hour  will  be  formulated  thus  : 

Q  per  hour-  (84200  -168400)Z>2. 

Here  D  is  in  metres.  The  coefficient  84200  corresponds  to  the 
capacity  for  flour,  and  168400  for  grain.  For  the  other  products  Q.  may 
be  obtained  by  substituting  the  corresponding  velocities  in  the  general 
formula. 

The  formula  we  are  suggesting  fairly  accurately  corresponds  to  the 
factory  data  of  capacity,  which  differ  from  our  calculations  by  1  to  3  per 
cent. 

Opposite  is  given  the  table  of  dimensions  and  capacity  of  the  worms 
from  Schmidt's  works  in  Wiirzen,  which  may  be  acknowledged  as  normal. 


CHAP.    VII] 


FLOUR   MILLING 


463 


TABLE    XLVIII 
DIMENSIONS  AND  CAPACITY  OF  WORMS 


d.—  Diameter  in 
mm. 

h.—  Pitch  in  mm. 

n.  —  Number  of 
Revolutions  per 
Minute. 

Q.—  Capacity  in 
Hectolitres  per 
1  Hour  of  Grain. 

Qi.—  Capacity  in 
Kilograms  per  1  Hour 
of  Flour. 

105 

110 

100 

23 

950 

115 

110 

100 

28 

1150 

130 

110 

100 

36 

1500 

140 

115 

100 

42 

1830 

150 

125 

80 

50 

2800 

170 

125 

80 

64 

3000 

190 

140 

80 

88 

4000 

210 

160 

70 

100 

4500 

250 

180 

70 

150 

6000 

270 

200 

70 

180 

7500 

300 

200 

60 

220 

9000 

330 

250 

60 

280 

11,000 

.  350 

250 

60 

310 

12,000 

400 

250 

50 

350 

14,000 

TABLE  XLIX 

DIMENSIONS  OF  AMERICAN  WORMS 


Diameter    of 
the  Worm  in 
Inches. 

Diameter  of 
the  Shaft  in 
Inches. 

Diameter  of 
the  Worm  in 
Inches. 

Diameter  of 
the  Shaft  in 
Inches. 

4 

1-0 

10 

2 

6 

1-5 

12 

2 

8 

1-5 

14 

2 

9 

1-5 

16 

2 

9 

2-0 

16 

3 

10 

1-5 

18 

3 

The  diameter  of  the  foundation  of  the  box  is  made  slightly  larger 
than  the  diameter  of  the  worm  by  2-5  mm.  (for  flour  and  grain).  The 
clearance  between  the  worm  and  the  box  must  be  a  little  larger  than  the 
largest  particle  of  the  transported  product,  otherwise  the  worm  would 
triturate  these  particles,  and  with  a  larger  clearance  the  dead  space  would 
increase.  ' 

Horizontal  Automatic  Conveyors. — The  ordinary  type  of  a  horizontal 
automatic  conveyor  is  shown  on  Fig.  465.  The  product  runs  to  the 
platform  P  (as,  for  instance,  in  filters),  over  which  there  pass  scrapers  t 
attached  to  two  endless  phains  g. 


464 


FLOUR   MILLING 


[CHAP,  vii 


Another  construction  of  the  same  principle  is  given  on  Fig.  466. 
Here  the  product  flows  into  tube-shaped  boxes  with  round  scrapers 
passing  through  them.  In  the  present  case  the  transmission  of  the  pro- 
duct is  effected  in  directions  lying 
at  right  angles.  The  transmitting 
action  is  easily  understood  from 
the  drawing.  At  the  other  ends 
of  the  boxes  there  are  two  belt- 
pulleys  like  B.  If  the  conditions 
of  space  require  it  another  con- 
veying belt -pulley  is  set.  The 
rope  used  for  the  traction  is  of  wire.  We  must  remark,  however,  that 
such  transport  is  used  by  the  Americans  for  small  coal  and  seldom  for  grain. 
On  Fig.  467  we  see  a  band  conveyor  for  sacks  forming  an  endless 
cloth  of  separate  timber  planks  attached  to  two  endless  parallel  chains 


FIG.  465. 


FIG.  466. 


which  run  on  four  pinions.  The  tension  is  adjusted  by  transposing  the 
bearing  of  the  pinions  lying  on  the  left,  which  is  done  by  turning  the 
hand-wheels  ra.  This  cloth  is  brought  into  play  from  the  belt-pulley  E, 
which  carries  a  second  pair  of  pinions  n  on  its  shaft.  To  reduce  friction, 
every  other  plank  there  is  an  idler  set  which  runs  in  guiding  rails. 


CHAP.    VII] 


FLOUR   MILLING 


465 


Band  Conveyor. — The  preceding  construction  of  an  endless  cloth 
serves  as  an  intermediate  step  to  the  band  conveyor,  which  has  become 
of  late  an  indispensable  appurtenance  of  grain  elevators  and  large  mills. 
The  general  idea  of  the  band  conveyor  is  shown  in  Fig.  468.  The 
endless  band  R  runs  over  two  belt-pulleys  D  and  Dl5  the  first  of  which  is 


FIG.  467. 

brought  into  action  by  the  driving  belt -pulley  N  ;  the  other  belt -pulley 
N1  is  loose.  The  band  is  supported  by  adjustable  idlers  from  above  and 
from  below.  The  grain  flows  down  S  through  the  hopper  A  and  is  carried 
by  the  band  to  the  "  throw-off  carriage  "  T,  on  which  there  are  two  guides, 
1  and  2,  with  the  band  running  over  them.  At  the  bend  of  the  band  over 
the  pulley  1  to  the  2nd  the  grain,  which  has  acquired  a  force  of  inertia, 
is  thrown  off  into  the  box  B,  whence  it  pours  down  the  spout  Slf  To 
tighten  the  band,  a  weight  G  with  a  pulley  3  is  suspended  to  it. 
The  method  of  throwing  the  stock  into  the  box  B  is  given  in  Fig.  469. 


FIG.  468. 

The  position  of  the  carriage  T  depends  on  the  place  where  the  product 
is  to  be  emptied.     By  means  of  brake  devices  it  is  fixed  to  the  spot. 

Different  construction  of  "  live  "  guide-pulleys  are  illustrated  on 
Figs.  470  and  471.  On  Fig.  470  we  have  a  set  of  top  and  bottom  pulleys 
supporting  the  band  R  ;  the  axes  of  the  top  idlers  are  inclined.  Guide- 
pulleys  with  inclined  axes  should  be  avoided,  as  the  bearings  do  not 
retain  the  oil  well. 

2G 


466 


FLOUR   MILLING 


[CHAP,  vn 


On  the  upper  drawing  on  Fig.  471  we  see  the  top  wooden  guide  with  a 
conic  turning  out.  The  incline  of  the  axes  of  the  pulleys  or  the  conic 
turning  out  or,  as  we  have  it  in  the  bottom  drawing,  the  globular  rims, 

are  needed  to  impart  a  trough-like 
shape  to  the  band,  which  prevents 
the  stock  from  falling  off  the  band 
on  its  travel. 

The  arrangement  of  the  top  and 
the  bottom  guides  (front  and  side 
view)  is  shown  in  Figs.  472  and 
473.  Here,  instead  of  the  globular 
guides  bending  the  belt,  we  have 
a  more  simple  construction — conic 
guide-pulleys.  The  top  part  of  the 
band  A  feeding  in  the  stock  is 
bent  by  these  belt -pulleys  to  a 
trough. 

Proceeding  now  to  consider  the 
operation  of  the  band  conveyors, 

we  must  point  out  the  relation  existing  between  the  velocities  of 
motion  of  the  product  and  the  diameter  of  the  guide-pulleys  1  and  2 
(Fig.  469). 

If  v  is  the  velocity  of  motion  of  the  band  (the  same  being  the  cir- 


FIG.  469. 


FIG.  470. 


FIG.  471. 


cumferential  velocity  of  the  pulley  1)  and  r  the  radius  of   the  pulley, 
the  value  of  v  is  defined  according  to  the  condition  : 


mv 


where  is  the  centrifugal  force  of  the  product  at  the  turning-point  of 

the  belt  to  the  pulley,  and  mg  the  gravity  of  the  stock.     To  prevent  the 


CHAP.    VII] 


FLOUR    MILLING 


467 


stock  from  running  off  the  band  before  it  reaches  the  top  point  A  of  the 
pulley  1,  we  must  accept =mg. 

Then  v  will  be  defined  thus  : 

v=  \/rg. 

The  maximum  value  of  v  will  be  defined  out  of  the  inequality  v  >  \lrcf, 
the  limit  for  v  being  the  condition  that  the  product  should  not  be  flung 
outside  the  bounds  of  the  box,  as  indicated  by  the  arrow  8.  But  this 
condition  is  indefinite,  therefore  it  is  better  to  accept  v—  *frg. 

Given  the  velocity,  the  r  of  the  guide-pulley  may  be  defined.  Gener- 
ally one  takes  a  radius  not  exceeding  the  values  0-40-0-64  of  a  metre. 
The  limit  largest  values  of  velocity  are  pointed  out  by  Professor  Fischer 


FIG.  472. 


FIG.  473. 


from  the  experimental  data   of    the   works    to   be   2-2-5   metres    per 
second. 

The  diameter  of  the  idlers  1-2  is  the  thickness  of  the  band  taken  25 
to  30-fold.  In  empiric  formulae  of  calculation  of  band  conveyors,  the 
breadth  of  the  band,  which  we  shall  name  B,  is  taken  as  modulus.  Mark- 
ing the  thickness  of  the  band  e,  we  deduce  the  following  value  for  it  from 
experimental  data  : 


The  breadth  B  of  the  band  varies  between  300  and  1000  mm. 

In  defining  the  capacity  of  band  conveyors  Professor  Fischer  accepts 
a  thickness  of  the  layer  of  grain  in  the  middle  of  the  band  not  exceeding 
^  of  the  breadth  of  the  band.  As  a  matter  of  consequence  the  area  of 
section  of  the  layer  of  product  is  defined  for  a  flat  band  as  the  area  of  a 
triangle  with  its  angles  at  the  base  equal  to  the  natural  angles  of  the  de- 
flection of  the  stock.  For  bands  of  a  trough-like  shape  of  section  (Fig.  472) 
that  area  is  expressed  by  the  area  of  a  trapeze  abed, 


468 


FLOUR   MILLING 


[CHAP,  vii 


Professor  Zworykin  suggests  the  following  areas  of  section  of  a  layer 
of  grain  : 

For  a  flat  band  .  /2  =0  -07£2. 

For  a  through-like  band       .          .          .          •     n,=Q-lB2. 


Once  the  area  of  section  of  a  layer  of  stock  on  the  band  and  its  velocity 
of  motion  are  known,  it  is  easy  to  define  the  capacity  Q  of  the  band 
conveyor,  which  will  be  expressed  thus  :  Q=O>v, 


CHAt>.  vn]  tfLOUR   MILLING  460 

The  consumption  of  power  must  be  defined  in  dependence  on  the 
tension  E  of  the  band,  which  is  taken  to  be  equal  to  1000.fi2  klgs. 

The  number  N  of  horse-power  for  a  band  conveyor  should  be  defined 
in  accordance  with  the  data  evolved  by  Professor  Petrov,  who  shows  in 
his  calculation  that  one  horse-power  carries  500  tons  a  distance  of 
1000  ft.  We  may  consider  that  one  horse-power  transfers  400-420  klgs. 
per  second.  Consequently,  N  will  be  formulated  thus  : 


N- 


400-420  ' 
Q  being  the  capacity  of  the  conveyor  per  second. 


APPARATUS  FOR  MIXING  AND  PACKING  FLOUR 

Flour-mixers. — Before  sending  the  flour  to  the  market,  it  is  necessary 
to  obtain  a  product  of  the  accepted  standard  as  regards  the  baking  quali- 
ties as  well  as  in  its  outward  appearance.  The  quality  of  the  grain 
depending  on  the  conditions  of  the  soil  and  the  climate,  the  manner  of 
treatment,  &c.,  is  very  inconstant,  and  this  naturally  affects  the  standard 
of  the  product.  Often  during  a  day's  run  of  a  mill  one  does  not  succeed 
in  obtaining  flour  of  a  certain  kind  uniform  in  quality.  That  being  the 
case,  one  is  obliged  to  blend  the  intermediate  grades  in  corresponding 
proportion,  to  obtain  the  kind  required. 

If  the  mill  works  for  eight  grades,  it  yields  from  twelve  to  fourteen 
in  its  grist.  These  grades,  except  the  first  two  or  three,  are  mostly 
medium,  and  because  of  their  insignificant  difference  in  quality  are  blended 
and  give  the  finished  product.  Sometimes  flour  of  better  grade  is 
admixed  to  the  inferior  ones  to  improve  their  quality,  if  they  are  below 
the  normal.  That  is. the  reason  of  the  constant  fluctuation  in  the 
percentages  of  yields  o£  flour,  especially  of  the  medium  grades.  The 
apparatus  used  for  mixing  the  flour  are  called  flour -blenders. 

The  flour -blenders  for  mixing  flour  are  divided  into  two  groups. 
Blenders  without  circulation  belong  to  one  of  them,  those  with  circula- 
tion belong  to  the  other. 

The  first  blenders  are  used  in  cases  where  the  intermediate  grades  of 
flour  obtained  at  different  times  of  the  day's  production  are  collected  in 
bins  or  sacks  according  to  uniformity,  and  are  taken  from  there  to  be 
fed  to  the  blender  in  a  certain  quantity  decided  upon  by  the  miller,  to 
obtain  directly  the  grade  required. 


470 


FLOUR   MILLING 


[CHAP,  vn 


The  second  type  of  blenders  has  such  a  construction  as  allows  of 
blending  without  interruption  the  flour  obtained  earlier  and  later,  owing 
to  their  circulatory  arrangement. 

Fig.  475  shows  a  simple  flour-blender  without  circulation.  An 
essential  part  of  this  flour-blender  is  the  disc  A  with  pins,  rotating  to- 
gether with  the  shaft  B  from  the  driving  belt-pulley  C.  Over  the  disc  A 

there  is  another  stationary  disc 
D  likewise  furnished  with  pins. 
These  discs,  as  well  as  the  cross 
bar  for  the  bearing  of  the  shaft, 
are  set  in  a  large  chamber  where 
the  blended  flour  collects.  Into 
the  hopper  E  simultaneously 
different  grades  of  flour  are  poured 
in  a  proportion  to  give  the  grade 
required.  That  flour  passes  to 
the  rotating  disc  A,  and  is  stirred 
between  the  pins.  The  disc  A 
runs  at  160  revolutions  per 
minute. 

The  defects  of  this  flour- 
blender  lie  in  the  fact  that  its 
disc  acts  as  a  suction  fan,  owing 
to  which  the  pressure  in  the 
chamber  rises  and  the  flour 
escapes  through  the  chinks  of  the 
chamber. 

Circulatory  Flour  -  blenders.  — 
On  Figs.  476  and  477  is  illustrated 
the  ordinary  type  of  a  circulatory 
blender  employed  nowadays.  The 
flour  flows  into  the  hopper  A  down  s,  whence  it  passes  to  the  worm  P, 
From  this  worm  it  goes  to  the  elevator  R,  which  carries  it  to  the  top  part  of 
the  blender  on  the  worm  N9  which  conveys  it  then  to  the  chamber  on  to  the 
agitators  T.  From  the  agitators  the  flour  again  passes  to  the  worm  P,  the 
elevator,  and  the  worm  N,  this  circulation  being  performed  until  a  finished 
uniform  product  is  obtained.  Then  the  spout  of  the  elevator  to  the 
worm  N  is  covered  over,  and  the  flour  directed  down  the  spout  S  to  the 
packer  G. 

The  construction  of  this  flour-blender,  which  is  a  modification  of  the 


FIG,  475. 


CHAP.    VIl] 


FLOUE   MILLING 


471 


old  Weber  Zeidler  blender,  belongs  to  the  works  of  Amme,  Giesecke  and 
Konegen,  but,  with  insignificant  variations,  is  also  built  by  other  works. 

On  Fig.  478  is  illustrated  one  of  the  latest  types  of  the  circulatory 
flour -blender,  the  construction  of  which  is  as  follows  : 

The  flour  runs  down  the  spout  a  and  falls  on  the  winged  stirrer  b, 
which  has  one  common  shaft  with  the  worm  c.  In  proportion  as  the 
flour  collects  at  the  bottom  of  the  chamber,  the  worm  enclosed  in  the 
pipe  d  lifts  it  up,  and  it  again  passes  to  the  stirrer  6.  When  the  flour 
is  sufficiently  mixed,  the  valve  e  is  opened  and  discharges  the  product. 


FIG.  476. 


FIG.  477. 


The  defects  of  this  blender  (the  forcing  of  air  into  the  chamber  by  the 
winged  fan)  are  the  same  as  in  the  simple  disc  blender  without 
circulation. 

Quite  recently  there  appeared  on  the  market  the  flour-blenders  of 
the  Gebr.  Meinecke  Works  in  Germany.  On  Fig.  479  may  be  seen  the 
more  simple  construction,  the  substance  of  which  is  almost  the  same  as 
of  the  blender  on  Fig.  478.  The  difference  is  that  in  the  hopper  A  there 
is  a  brush  apparatus  E  which  reduces  the  cakes  and  clots  of  flour  before 
it  passes  into  the  chamber  B.  The  worm,  which  is  driven  from  a  gear 
drive  with  the  aid  of  a  driving  belt-puUey  D,  has  two  different  diameters. 
At  the  lower  pipe  of  the  worm  is  suspended  a  conic  shaker  F.  At  the  top, 


472 


FLOUR   MILLING 


[CHAP,  vii 


on  the  shaft  of  the  worm,  there  is  fitted  a  brush  stirrer  G  which  reduces  the 
flour  and  throws  it  off  the  flange  of  the  pipe  of  the  top  part  of  the  worm. 

When  the  flour  is  sufficiently  blended,  it  is  de- 
livered through  the  boss  C  by  opening  the  valve. 
On  Fig.  480  may  be  seen  a  blender  with  a 
more  complete  circulation.  The  flour  is  de- 
livered into  the  hopper  A,  where  there  is  a 
brush  apparatus  and  a  worm,  as  we  shall  see 
further  on ;  from  the  hopper  it  flows  into  the 
elevator  B  which  carries  it  to  the  chamber  of 
the  blender,  where  it  can  circulate  just  as  in  the 
blender  (Fig.  479)  or  be  conveyed  by  the  worm 
D  again  to  the  elevator  B,  if,  by  means  of 
the  rod  E,  the  gate  valve  of  the  boss  of  the 
outlet  in  the  chamber  is  opened.  When  the 
flour  is  sufficiently  blended,  the  spout  is  covered 
over  by  the  valve  F  out  of  the  elevator  into 
the  blender,  and  the  product  directed  into  the 
spout  G  for  packing. 
Figs.  481  and  482  illustrate  a  flour-blender  from  the  same  works 
with  a  vertical  worm  instead  of  an  elevator.  Fig.  482  exhibits  the  hopper 


FIG.  478. 


FIG.  480. 


A  in  section,  showing  that  it  contains  a  brush  apparatus  B  and  a  hori- 
zontal worm  C,  which  conveys  the  stock  to  the  vertical  worm  D. 


FLOUR   MILLING 


473 


CHAP,  vn] 

Packing  the  Flour. — -For  flour  which  has  to  stand  a  lengthy  trans- 
portation or  lie  a  long  time  in  warehouses,  packing  is  of  the  greatest 
importance.  In  America  flour  is  packed  almost  exclusively  in  barrels, 
and  only  small  quantities  from  30  to  60  Ib.  are  packed  in  sacks  of 
cotton. 

Although  barrel  packing,  where  the  flour  is  first  put  in  a  sack  and 
then  with  the  sack  into  the  barrel,  is  considerably  more  expensive,  its  ad- 
vantages are  very  great.  The  caking  of  flour  packed  in  barrels  is  totally 


FIG.  481. 


FIG.  482. 


obviated,  since,  when  stored  in  large  masses,  the  pressure  falls  upon  the 
barrels  and  does  not  affect  the  flour. 

In  Western  Europe  and  Russia  flour  is  packed  exclusively  in 
sacks,  and  consequently  the  heaping  of  sacks  in  large  stacks  is  very 
dangerous,  especially  for  a  slightly  damp  flour,  which  cakes  up  and 
becomes  heated. 

The  ordinary  simple  way  of  sacking  the  flour  is  performed  by  hand 
through  the  delivery  spout.  This  method  is  satisfactory  when  the 
capacity  is  small,  but  cannot  be  adopted  in  large  mills  in  which  special 
flour  packers  are  used. 


474 


FLOUR   MILLING 


[CHAP,  vn 


In  Fig.  483  is  shown  the  Amme,  Giesecke  and  Konegen  packer, 
which  differs  but  slightly  from  similar  apparatus  of  other  firms .  Its  nature 
is  as  follows  : 

.  The  flour  passes  down  the  spout  S  to  the  auger  A,  in  which  there  is  a 
worm  with  a  downward  run  of  the  flour.  The  worm  is  brought  into 
action  by  a  bevel  gear  system  from  the  belt-pulley  B,  which  is  thrown  in 
by  the  friction  clutch  C.  On  the  auger  A  there  runs  freely  the  boss  D, 
to  which  a  sack  is  attached  by  means  of  a  strap  with  a  French  clasp. 
The  boss  D  is  suspended  on  straps  E  (or  on  chains),  which  are  wound  on 


L 


H 


FIG.  483. 


FIG.  484. 


drums  F.  The  boss  is  balanced  by  a  weight  H,  because  F  and  G  are 
coupled  by  a  rope  or  belt  gear. 

The  sack  is  lifted  at  first,  enveloping  the  auger  A,  and  then,  in  propor- 
tion as  it  is  packed,  it  drops  down.  During  operation  the  worm  dis- 
charges the  product  out  of  the  auger  into  the  sack,  and  when  the  sack  is 
full,  the  same  worm  adds  more  flour  and  presses  it  down  with  its  weight 
to  the  required  compactness. 

The  rod  L  runs  to  the  brake  which  regulates  the  lowering  of  the  sack — 
in  other  terms,  the  degree  of  compactness  of  the  packing. 

In  Fig.  484  we  have  Baverio's  packer  of  a  similar  type,  with  an 
adjustable  platform  A  for  supporting  the  sacks.  The  lifting  and  lowering 
of  the  platform  is  done  by  means  of  chains  (there  are  two  chains  for  the 
sake  of  equability)  winding  on  or  off  drums.  The  weight  of  the  platform 


FLOUR   MILLING 


475 


CHAf.    VIl] 

is  counterbalanced  by  the  weight  Q.  For  skidding  a  band  brake  B  is 
provided.  The  motion  of  the  worm  is  received  by  the  bevel  gear  from 
the  driving  pulley  C  which  is  rotated  from  the  counter  shaft  with  a  loose 
belt -pulley. 

American  Packers. — Fig.  485  shows  the  Nordyke  &  Marmon  Co. 
flour  packer.  The  discharge  worm  is  brought  into  action  from  a  bevel 
gear,  which  may  be  thrown  on  and  off  by  means  of  the  friction  clutch  a. 
For  packing  sacks  of  various  sizes  there  are  augers  of  different  diameters 


FIG.  485. 


FIG.  486. 


with  conic,  funnel-shaped  ends,  by  which  they  are  fixed  to  the  discharge 
tube  of  the  apparatus.  At  the  end  of  the  discharge  worm  is  attached  a 
ramming  worm  with  one  pitch.  The  diameter  of  this  worm  is  altered 
in  accordance  with  the  size  of  the  sack.  The  sack  lift  is  suspended  on 
chains,  which  are  wound  on  and  off  a  drum  with  a  brake  pulley. 

The  number  of  revolutions  of  the  worm  per  minute  is  200.  The 
weight  of  the  sacks  packed  may  be  from  20  to  200  lb.,  the  number  of 
sacks  from  70  to  100  per  hour. 

On  Fig.  486  we  see  a  packer  for  bran  with  the  auger  set  the  funnel- 
shaped  end  downwards.  Since  it  is  necessary  to  ram  the  bran  down  hard 


476 


FLOUR   MILLING 


[CHAP,  vii 


the  sack  is  placed  in  an  iron  casing  A,  otherwise  it  might  burst.  After 
the  packing  operation  is  over  the  casing  is  opened  and  the  sack  removed 
from  the  lift. 

The  number  of  revolutions  of  the  discharge  worm  is  200  per  minute, 
the  capacity  50  to  60  100-lb.,  or  35  to  40  200-lb.  sacks  per  hour. 


VI 

APPARATUS  FOR  RECKONING  AND  REGULATING  THE  QUANTITY  OF 

PRODUCT 

Automatic   Scales.—  The   apparatus   which   serve   for  reckoning  the 
quantity  of    grain  stock  are   constructed  for  dry  substances  generally, 


FIG.  487. 


FIG.  488. 


FIG.  489. 


and  their  purpose  is  automatically  to  weigh  the  product  flowing  in  with- 
out interruption  to  be  treated  or  packed. 

The  most  typical  representatives  of  this  kind  of  apparatus  are  the 
scales  "  Chronos,'  "  Libra,"  &c. 

Figs.  487,  488,  and  489  illustrate  the  plan  of  the  "Chronos"  scales, 
and  the  essence  of  their  construction  consists  in  the  following.  There 
is  a  cast-iron  frame  AL  on  which  the  hopper  D  for  the  product  is  set. 
This  hopper  is  divided  by  the  partition  a2  with  a  slot,  in  which 
there  runs  the  valve  gate  dl  connected  by  a  system  of  levers  with 
the  balance  levers.  On  the  right-hand  side  of  the  balance  levers  or 
scale  beam«  A  and  /  is  set  a  scale  C  for  weights,  on  the  left  on  rods  b  is 
suspended  the  scale  B,  which  rests  with  steel  prisms  d,  set  into  the  jour- 
nals of  the  scale.  The  beams  A  and  /  rest  with  their  steel  prisms  on  steel 
linings  in  the  brackets  of  the  frame.  To  the  beam  A  is  attached  an  arm 
Z  which  indicates  the  correct  setting  of  the  scales  when  in  vertical  position. 


CHAP.    VII 


FLOUR    MILLING 


477 


FIG.  490. 


Through  the  left-hand  side  part  aL  of  the  hopper  D,  the  grain  runs 
into  the  scale  B,  then  the  right-hand  side  a  is  covered  with  the  gate  d^ 
When  the  scale  is  sufficiently  filled  with  grain,  it  drops  down  and  upsets, 
assuming  the  position  Blt  and 
the  grain  quickly  pours  out. 
At  the  same  time  the  lever  #, 
connected  with  the  scale  (see 
perspective  view)  and  with  the 
meter  x,  drops  down  and  turns 
one  division  of  the  pinion  of  the 
counting  mechanism.  Simul- 
taneously with  the  dropping  of 
the  scale  the  valve  F  closes  the 
outlet  of  the  hopper.  When 
the  grain  has  run  out,  the 
weights  return  the  scale  to  its 
former  position,  to  take  the 
next  load  of  grain,  £c. 

In  the  perspective  view  (Fig.  488)  is  shown  the  lever  with  the  adjust- 
able weight  for  accurately  mounting  the  scales. 

In  Fig.  489  we  see  the  scale  "  Libra,"  which  differs  from  the  "  Chro- 

nos  "  in  small  details. 

When  mounting  the 
scale  it  is  enclosed  in  an 
iron  case,  which  is  locked 
or  sealed,  to  prevent  the 
workmen  from  altering 
the  number  indicated 
for  the  purpose  of  cheat- 
ing. The  chamber  in 
which  the  scale  is  en- 
closed must  always  be 
exhausted,  otherwise 
the  delicate  cranks  of 
the  scale  beams  and  sys- 
tems of  levers,  having 
become  dusty,  cease 


FIG.  491. 


working  accurately  and  the  balance  begins  to  show  incorrect  weights. 

Fig.  490  illustrates  a  perspective  view  of  the  "  Chronos  "  scale,  and 
Fig.  491   a   perspective  view  of  the  "  Libra "  scale,  which  is  slightly 


478 


FLOUR   MILLING 


[CHAP,  vn 


different  from  the   "  Chronos  "   in   its  construction,  but    gives  just   as 
accurate  a  weighing. 

Columbian  Feed  Governor.— for  regulating  the  quantity  of  product 
fed  to  the  roller  mills,  the  American  apparatus  "  Columbia  "  is  employed. 
It  consists  of  a  box  A  (Fig.  492),  through  the  inclined  wall  of  which 
there  is  made  an  opening  E.  In  the  opening  E,  attached  to  the  lever  F, 
there  is  a  slide  valve  G,  by  raising  or  lowering  which  the  quantity  of 
grain  passing  through  this  opening  is  increased  or  reduced.  When 
dropped  to  the  bottom,  the  slide  valve  G  closes  the  opening  E,  but 
only  so  far  as  to  allow  passage  to  the  least  flow  of  the  apparatus  of  any 

given  size. 

The  automatism  of  action 
and  adjustability  of  this  ap- 
paratus consist  in  the  following. 
The  lever  F  in  its  axis  of 
rotation  is  fixed  by  hook-like 
rings  MM,  and  by  means  of  a 
solid  rod  is  coupled  with  the 
lever  C. 

On  one  side  of  the  lever  C 
there  are  two  counterweights, 
the  larger  of  which  is  sta- 
tionary, while  the  smaller  one 
T  freely  travels  over  the  rack 
part  of  C.  By  setting  this 
adjustable  counterweight  T  on  a  corresponding  grade  marked  on  the 
scale  of  the  lever  C.  the  quantity  of  product  running  per  minute 
through  the  opening  E  is  determined.  The  lever  C,  on  the  side 
opposite  to  the  counterweights,  has  two  handles  88,  to  the  ends  of 
which  on  wire  rods  a  frame  B  with  inclined  planes  K  is  suspended. 
The  grains  falling  on  the  inclined  planes  K  produce  a  pressure  which 
imparts  motion  to  the  lever  C  and  through  it  effects  a  corresponding 
alteration  on  the  position  of  the  slide  valve  G  fixed  to  the  lever  F. 

To  attain  a  quiet,  even  action  of  the  slide  valve  G  there  is  a  piston  J 
running  in  a  cylinder  /  with  glycerine  and  connected  with  one  of  the 
handles  S  of  the  lever  C.  .  If  the  apparatus  is  designed  to  do  service  for 
a  double  roller  mill,  i.e.  a  roller  mill  with  two  pairs  of  rolls,  it  has  to  be 
stationed  in  the  middle  of  the  roller  mill  hopper,  so  that  the  frame  B 
should  be  placed  down  the  length  of  the  rolls.  But  if  the  grain 
runs  only  to  one  pair  of  rolls,  the  apparatus  is  set  over  the  hopper, 


FIG.  492. 


CHAP.    VII] 


FLOUR    MILLING 


479 


so   that  the    counterweights  are   opposite  to  the  feeding  spout  of   the 
mill. 

In  mounting  the  apparatus  particular  attention  should  be  paid,  that 
it  is  fixed  on  the  hopper  of  the  roller  mill  perfectly  accurately  in  vertical 
and  horizontal  position,  otherwise  it  will  either  operate  badly  or  leave  off 
working  altogether. 

The  inlet  aperture  in  the  hopper  of  the  roller  mill  is  made  5  mm. 
larger  in  length  and  width  than  the  outlet  of  the  apparatus.  The  spout 
conveying  the  stock  has  to  be  set  if  possible  not  vertically  but  aslant. 
If  the  position  of  the  spout  is  vertical  several  plates  lying  across  each 
other  should  be  set  in  it  and  receive  the  blows  from  the  grain  passing 
through.  It  is  still  better 
in  such  a  case  to  fit  directly 
under  the  apparatus  in  the 
outlet  spout  a  slide  valve, 
by  means  of  which  the 
inflow  of  grain  may  be 
stopped,  if  there  is  anything 
to  be  put  into  order,  or  a 
part  of  the  mill  has  to  be 
inspected. 

On  Fig.  493  is  given  a 
perspective  view  of  this  ap- 
paratus. 

Before  starting  the  ap- 
paratus all  movable  parts 
must  be  examined  to  be  sure  that  they  work  freely.  The  cylinder  / 
must  be  filled  with  glycerine  to  a  level  5  mm.  from  the  top  lid  ;  generally 
the  glycerine  is  never  added  afterwards. 

Before  letting  the  grain  into  the  apparatus,  the  adjustable  counter- 
weight T  is  set  on  the  division  of  the  lever  C  corresponding  to  the  passage 
of  the  required  quantity  of  stock. 

When  the  apparatus  is  in  operation,  the  feeding  rolls  and  the  feeding 
slide  valve  have  to  be  so  far  open  that  the  grain  may  pass  through  un- 
hindered, and  not  collect  under  the  frame  B,  otherwise  the  action  of  the 
apparatus  will  be  incorrect. 

If  the  handles  SS  of  the  lever  G  fall  on  the  block  A  when  the  least 
quantity  is  being  treated,  then,  to  make  the  operation  of  the  apparatus 
correct,  the  rod  is  slightly  shortened  by  bending. 

When  cleaning  the  slide  valve  G  or  the  passages  between  the  inclined 


FIG.  493. 


480  FLOUR    MILLING  [OHAJ>.  vn 

plates  K  (in  the  frame  B)  only  wooden  tools  should  be  used,  and  in  no 
case  sharp  metal  ones.  The  pear-shaped  weight  V,  given  in  addition  to 
each  apparatus,  is  set  on  one  of  the  handles  S  of  the  lever  C  when  it  is 
necessary  to  close  the  opening  E  completely. 


VII 

FLOUR  BLEACHING 

Owing  to  the  great  development  of  milling  technics  during  the 
last  ten  years,  it  has  been  shown  that  it  is  possible  to  obtain  products 
of  a  perfection  not  conceived  previously.  The  attempts  to  improve 
the  outward  qualities  of  flour  referred  to  its  colour  as  well.  We  must 
acknowledge  that  the  consumer  very  soon  became  used  to  the  grades  of 
flour,  which  are  of  a  better  colour,  for  instance,  and  is  extremely  parti- 
cular about  it.  The  desire  of  the  mills  to  comply  with  these  demands 
forced  them  to  have  recourse  to  a  chemical  action  upon  the  flour  with  the 
view  to  improving  its^  white  colour  ;  the  other  grounds  adduced  in 
explanation  of  this  manipulation,  such  as  enhancing  the  baking  qualities 
of  the  flour,  &c.,  being  only  of  secondary  importance. 

The  improvement  in  the  white  colour  of  the  flour  may  be  attained  by 
treating  it  with  bleaching  substances.  It  is  evident  that  a  series  of 
bleaching  materials  has  to  be  excluded  as  injurious  in  this  operation, 
and  only  those  may  be  applied  which  are  volatile  and  may  be  extracted 
after  they  have  had  their  effect  on  the  flour.  Such,  for  instance,  are  all 
gases  which  have  a  bleaching  effect  on  the  organic  substance  :  chlorine, 
sulphureous  gas,  ozone,  oxides  of  nitrogen. 

On  the  ground  of  previous  experience  as  to  the  effect  of  these  sub- 
stances upon  flour  the  following  is  known  :  though  chlorine  and  sul- 
phureous gas  do  bleach  the  flour  they  lower  its  quality  so  much  as  to  make 
them  commercially  impossible.  Ozone  likewise  bleaches  the  flour  but 
imparts  an  unpleasant  odour  to  it.  Thus,  the  sole  adaptable  bleaching 
substances  remaining  are  the  nitrogen  peroxides. 

The  Alsop  Bleaching  Process. — In  1903  Alsop  patented  his  process  of 
flour  bleaching  by  means  of  electrified  air  in  apparatus  especially  invented 
for  the  purpose. 

Alsop's  apparatus  (Fig.  494)  consists  of  four  parts  :  a  dynamo,  an 
induction  coil,  an  air  pump  for  electrification,  and  a  switchboard.  The 
electrifying  pump  is  the  most  important  part  of  the  whole  system ;  in  it 
the  bleaching  gases  are  produced.  Between  two  couples  of  electrodes 


CHAP.   VII] 


FLOUR   MILLING 


481 


there  is  a  constantly  interrupted  contact,  owing  to  which  electric  sparks 
7  to  15  cm.  long  are  caused.  Under  the  effect  of  these  sparks  chemical 
re-actions  take  place  between  the  nitrogen  and  the  oxygen  of  the  air,  which 
give  NO2,  nitrogen  dioxide.  The  electrode  couples  are  placed  in  tubes 
A  A,  one  of  the  electrodes  in  each  being  set  fast  on  the  bottom  of  the  tubes, 
while  the  others  move  in 

the  tubes  with  the  aid  of  -  11/7 

slide  rods  EE.  The  slide 
rods  are  connected  with 
each  other  in  such  a  way 
that  they  alternately  ap- 
proach the  upper  elec- 
trodes to  the  bottom  ones 
and  remove  them,  owing 
to  which  electric  sparks 
are  formed  between  the 
electrodes. 

The  apparatus  operates 
in  the  following  manner  : 
with  the  aid  of  the  double 
action  pump  B  a  current 
of  pure  air  is  by  turns 
aspirated  through  the 
inlets  HH.  In  the  tubes 
A  A  the  air  is  subjected  to 
the  action  of  the  electric 
sparks.  The  aspiration 
of  air  takes  place  simul- 
taneously with  the  pro- 
duction of  a  spark.  The 
electrified  air  is  conveyed 
through  the  tubes  CC 
away,  and  flows  through 

valves  into  the  chamber  B,  whence  through  the  connecting  pipes  and 
valves,  set  in  the  back  wall  of  the  chamber  (not  seen  in  Fig.  494),  it 
passes  into  the  pipe  which  conducts  to  the  apparatus  in  which  the  flour 
is  agitated.  Further,  the  marks  on  the  figure  denote  :  DD  wires  for  the 
current,  0  the  sliding  rod  of  the  pump  piston,  and  F  the  shaft  on  which 
a  pulley  of  any  particular  diameter  for  driving  the  apparatus  may  be  set. 

The  agitating  apparatus  has  the  shape  of  an  oblong  drum  in  which  the 

2H 


FIG.  494. 


482  FLOUK    MILLING  [CHAP,  vn 

flour  is  kept  in  constant  motion  by  a  system  of  beaters  ;  owing  to  this  the 
particles  of  flour  come  well  in  contact  with  the  electrified  air.  The  effect 
of  the  gases  becomes  manifest  after  about  a  minute's  stirring  of  the  flour. 

The  operation  of  the  apparatus  may  be  regulated.  First  of  all,  the 
quantity  of  air  introduced  may  be  altered  through  a  special  globe  valve  ; 
the  tension  of  the  current  and  its  quantity  can  likewise  be  altered. 

Experiments  of  bleaching  after  Alsop's  method  were  performed  with 
a  strength  of  current  of  5,  6,  7,  8,  and  9  amperes.  The  stirring  apparatus 
treated  36  to  40  sacks  per  hour  ;  the  flour  passed  through  the  drum 
in  the  space  of  1 J  minutes  and  was  consequently  under  the  effect  of  these 
gases  only  during  that  time.  Neither  in  the  drum  nor  on  leaving  it 
did  the  flour  smell  of  the  gases.  Three  kinds  of  flour  were  tested.  They 
were  all  obtained  from  Argentina  wheat,  which  was  just  then  being 
treated  at  the  mill.  The  following  were  the  grades  : 

Patent  wheat  flour  .          .          .          .  0  to  30  per  cent. 

Bakers'      „         „     ,         ....     30  to  64-5     „ 
Low  grade  ,,       ,,     .          ....     64-5  to  73      „ 

The  experiments  were  commenced  with  a  current  5  amperes  strong. 
It  appeared  that  with  such  a  strength  of  current  it  was  impossible  to 
notice  any  visible  change  in  the  flour  definable  by  pekarisation.  Only 
beginning  with  6  amperes  did  the  effect  of  the  gases  upon  the  patent  and 
bakers'  flour  become  manifest,  and  then  grew  more  intense  with  the 
increasing  strength  of  the  current.  Before  it  was  bleached  the  flour  had 
that  peculiar  colour  which  is  demanded  in  Germany  in  good  wheat  flour, 
or,  at  least,  is  very  much  appreciated.  That  colour  remained  after 
bleaching  with  5  amperes  unchanged  ;  with  6  amperes  it  was  per- 
ceptible, but  seemed  already  to  be  a  little  lighter  ;  with  7  amperes  it 
was  scarcely  noticeable  ;  on  the  contrary,  the  flour  began  to  assume  a 
kind  of  dead  grey  colour,  which  with  the  further  increase  in  the  strength 
of  the  current  grew  more  intense. 

The  effect  of  the  gases  appears  to  have  been  greater  on  patent  flour 
than  on  bakers'.  The  patent  flour  when  more  strongly  bleached  assumes 
a  colour  reminding  one  of  the  colour  of  chalk,  whereas  the  bakers'  flour 
assumes  a  dead  greyish-white  colour.  This  difference  is  particularly 
visible  by  "  Pekar's  "  test. 

As  to  the  low  grades  flour,  the  nitrogen  peroxide  seems  to  have  no 
effect  upon  it.  Even  after  a  strong  bleaching  with  a  current  8  amperes 
strong  one  could  not  discover  by  dry  test  any  alteration,  while  the  wet 
test  showed  a  slight  difference  in  colouring.  The  low  grade  flour  is 
practically  unbleachable. 


CHAP.    VII] 


FLOUR   MILLING 


483 


Other  Bleaching  Processes. — Besides  Alsop's  process  there  are  other 
methods  of  flour  bleaching.  In  all  cases  the  bleaching  agent  is  nitrogen 
dioxide  (NO2).  The  various  processes  of  bleaching  differ  from  each 
other  only  in  the  manner  in  which  the  bleaching  gas  is  obtained.  This 
is  done  in  different  manners — by  electrifying  the  air,  or  as  in  one  of  the 
processes,  chemically. 

Two  other  processes  belong  one  to  the  Ozonised  Oxygen  Co.,  Ltd., 
and  the  other  to  the  Flour  Oxidising  Co.,  Ltd.  Both  the  companies  put 
the  building  of  the  apparatus  into  the  hands  of  Henry  Simon  in  Manchester. 
In  the  description  of  the  Ozonised 
Oxygen  Co.  ozone  is  erroneously 
considered  to  be  the  bleaching 
gas  ;  this  idea  found  its  way  into 
the  name  of  the  company.  In 
reality  the  bleaching  gas  here  is 
also  the  nitrogen  dioxide  obtained 
through  the  discharge  of  a  high 
tension  current.  As  we  see  in 
Fig.  495,  in  the  top  part  of  the 
iron  cupboard,  where  the  whole 
system  is  placed,  there  is  a  glass 
tube  A  with  six  electrode  couples, 
between  which  the  electric  dis- 
charges take  place.  Into  this 
tube  by  means  of  a  fan  is 
drawn  the  fresh  air,  which  is 
then  forced  into  the  air  tank, 
whence  it  is  directed  to  the  drums 
M,  where  the  feeding  in  and 
the  stirring  of  the  flour  undergoing  the  bleaching  process  is  performed. 

The  experiments  were  made  in  London  at  one  of  the  mills,  where  the 
system  described  operates  with  a  steady  strength  of  current  of  15  to  17 
amperes.  The  flour  is  bleached  in  six  parallel  drums,  and  remains  under 
the  influence  of  the  N02  for  only  about  one  minute. 

The  bleached  product  the  investigators  treated  was  a  flour  from 
the  following  mixture  :  eight  parts  of  Russian  wheat,  three  parts  of 
Australian,  four  of  North  Manitoba,  four  of  La  Plata,  and  eight  parts  of 
hard  winter  wheat  (North  America).  The  flour  was  of  the  first  grades 
to  the  amount  of  35  per  cent,  A  similar  unbleached  flour  served  for 
comparison, 


FIG.  495. 


484 


FLOUR   MILLING 


[CHAP,  vn 


The  experiments  performed  with  these  products  gave  no  signs  of  the 
properties  and  the  baking  qualities  of  the  bleached  flour  being  modified. 
Contrary  to  former  observations,  however,  it  was  established  that  not 
only  the  bleached  flour,  but  the  crumb  of  the  bread  made  of  it  as  well, 
appeared  to  be  whiter.  Nevertheless,  the  differences  were  insignificant, 
and  could  be  noticed  only  when  directly  compared. 

In  the  plant  of  the  Flour  Oxidising  Co.'s  bleaching  apparatus  the 
bleaching  gas  is  procured  chemically.  Small  quantities  of  ammonia 
gas  are  conveyed  through  a  red-hot  platinum  tube,  and  thus  the  nitrogen 
dioxide  obtained.  As  is  shown  on  Fig.  496,  a  large  quantity  of  air  is 
forced  with  the  aid  of  an  air  pump  and  reservoir  into  the  tube  generating 


FIG.  490. — Bleaching  Apparatus  of  the  Flour  Oxidising  Co.,  Ltd. 

A— air  pump  ;  B— reservoir  for  air  ;  C— cylinder  for  ammonia ;  D— nitrogen  dioxide 
(N02)  generator;  ^-reservoir  for  NO.,;  M  -drum  for  flour;  F— flour  feed; 
G — bleached  flour  delivery. 

the  nitrogen  dioxide,  where  those  two  gases  blend  and  are  directed  to 
the  bleaching  drums. 

The  gases  forming  in  the  electric  arc  lamp  can  also  serve  for  flour 
bleaching.  Besides  the  various  oxygen  combinations  of  carbon  (CO  and 
CO  2)  in  the  voltaic  arc  there  are  also  formed  oxides  of  nitrogen,  and 
among  them  the  nitrogen  dioxide  (NO2)  possessing  bleaching  properties. 
Owing  to  the  high  temperature  of  the  voltaic  arc,  the  gases  appearing 
are  immediately  destroyed  ;  but  if  the  air  out  of  the  arc  lamp  is  being 
steadily  sucked  away,  a  mixture  is  obtained  consisting  chiefly  of  air, 
though  the  above.-namevd  gases  are  present  in  sufficient  quantity  to  have 
a  bleaching  effect.  Especially  convenient  for  that  purpose  are  the  arc 
lamps  where  the  carbons  are  set  not  opposite  to  each  other  but  form  a 
sharp  angle,  as  is  the  case^  for  instance,  in  the  arc  lamps  for  continuous 


CHAP,  vn]  FLOUR    MILLING  485 

current  manufactured  by  the  Arc  Lamp  Works,  Ltd.,  in  Nurnberg. 
Such  lamp£  are  easily  joined  into  one  system  by  means  of  a  reservoir. 
If  the  electrified  air  were  to  be  drawn  out  of  this  reservoir,  it  could  be 
directed  after  cooling  in  the  air  tank  to  the  bleaching  drums. 

General  Results  of  Investigation. — The  results  of  Buchwald  and  Neu- 
mann's experiments  lead  to  the  conclusion  that  the  normal  bleaching 
does  not  cause  any  great  change  of  a  chemical  character.  Attention 
must  be  especially  drawn  to  the  fact  that  even  after  a  lapse  of  several 
months  a  test  of  the  flour  gave  the  same  results  ;  consequently,  the 
bleached  flour,  even  in  the  course  of  time,  shows  no  tendency  to  modifica- 
tion. At  the  same  time  it  was  established  that  the  bleaching  effect  of 
the  nitrogen  dioxide  is  based  on  the  modification  of  the  fat  in  the  wheat 
flour.  Fleurent  considers  that  the  nitrogen  oxide  precipitates  directly 
on  the  fat,  since  it  disappears. 

According  to  Avary  and  to  Alway  and  Pinkney  the  oxides  of  nitro- 
gen decolorise,  in  the  same  way  as  sunlight,  the  colouring  substance 
dissolved  in  the  fat  of  the  wheat. 

The  fat  obtained  by  Buchwald  and  Neumann  out  of  bleached  flour, 
the  raw  fat  of  ether  extraction,  displayed  no  changes  in  colouring.  The 
benzol  extract  proved  to  be  lighter  only  in  a  strongly  (9  amperes)  bleached 
flour.  In  optical  respect  the  fats  showed  no  deflections.  The  quanti- 
tative differences  in  the  contents  of  fat  are  caused  by  bleaching  appar- 
ently only  in  the  patent  flour,  the  quantity  of  flour  soluble  in  ether  at 
the  same  time  increasing,  but  also  here  the  differences  are  insignificant.  In 
the  bakers'  grades,  where,  owing  to  the  larger  percentage  of  fat,  greater 
modifications  would  be  expected,  there  were  likewise  no  differences  noticed. 

In  its  fresh  condition  and  after  it  had  been  lying  the  flour  contained 
the  same  amount  of  water.  Neither  was  there  any  difference  notice- 
able in  the  quantity  of  acid. 

The  diastatic  power  of  flour,  manifest  in  its  property  of  converting 
to  sugar,  apparently  increases  in  case  of  a  weak,  i.e.  normal  bleaching, 
and  drops  when  that  process  is  exaggerated. 

An  important  point  in  the  inventor's  methods  is  the  assertion  that 
the  quantity  of  protein  in  the  flour  increases  owing  to  his  method 
of  bleaching,  while  the  amount  of  carbo-hydrates  diminishes.  The  truth 
of  such  an  assertion  seems  incredible,  but  it  is  interesting  to  watch 
the  effect  the  bleaching  gases  have  on  the  amount  of  nitrogen  and  gluten 
in  the  flour. 

From  the  results  of  Buchwald  and  Neumann's  experiments  the 
following  may  be  inferred  :  the  quantity  of  nitrogen  remains  the  same 


436 


FLOUR   MILLING 


[CHAP.  Vli 

if  the  bleaching  is  weak,  but  it  diminishes,  especially  in  the  bakers'  grades, 
if  the  bleaching  is  strong.  An  analogous  phenomenon  was  observed  in 
the  gluten.  The  differences  in  the  amount  of  gluten  proved  to  be  in- 
significant owing  to  the  inaccuracy  of  the  method  of  investigation,  but 
must  be  regarded  as  correct,  since  the  numbers  obtained  in  the  manifold 
repetitions  of  the  investigation  were  the  same. 

Out  of  these  experiments  the  following  numbers  were  obtained  : 

TABLE   L 


1 

i 

Patent. 

Bakers'  Grades. 

•  i 

Unbleached. 

Bleached.  . 

Unbleached 

Bleached. 

6  Amp. 

9  Amp. 

6  Amp. 

9  Amp. 

Water     .      .      . 

.        .        .        10 

•59 

10-30 

10-28 

10-57 

10-38    10-4 

Fat    .... 

.        .        .           0 

•89 

1-25 

1-12 

1-29 

1-30      1.16 

Total  quantity  of 
Proteins  dissolved 

proteins  !    1  1 
in  water       2 

•50 
•35 

11-80 
1-80 

11-42 
2-75 

12-18 
1-89 

12-18 
1-81 

11-18 
2-55 

Gluten    .      .      . 

.  .    .      .      10 

•60 

11-00 

10-20 

12-00 

12-00 

10-80 

Sugar  (maltose) 

.      .      .        0 

•97 

0-71 

0-81 

0-74 

0-75 

1-01 

Diastatic  power 

.      .      .      19 

•2 

23-8 

18-2 

21-7 

29-0 

19-6 

The  results  obtained  from  experiments  in  baking  have  the  most 
weight  for  practice. 

The  flour  the  investigators  had  at  their  disposal  was  tested  in  accurate 
laboratory  experiments  as  well  as  practically  in  baking  establishments  ; 
both  the  results  coincide  well.  There  were  no  advantages  or  defects 
discovered  in  the  bleached  flour. 

In  no  case  was  the  bleached  flour  found  to  be  worse  as  regards  the 
baking  qualities. 

The  experiments  were  so  arranged  as  to  have  the  process  of  fermenta- 
tion, on  the  one  hand,  take  place  in  particularly  favourable  circumstances 
in  the  laboratory  experiment — and  on  the  other  hand,  in  the  conditions 
obtaining  in  practice.  It  appeared  that  the  water-absorbing  capacity  of 
bleached  flour  is  slightly  smaller ;  the  quantity  of  water  being  the  same, 
a  larger  amount  of  flour  was  necessary  to  prepare  the  same  dough. 


'nbleached. 


Bleached. 
6  amp.  9  amp. 

1-460       1-440 
1-726       1-692 


Quantity  of  water  required  by  patent  flour      .   1-380 
»  »  »  bakers' grades  .    1-640 

In  other  words,  bleached  flour  absorbs  less  water,  viz.  : 

Patents    V  ,        \          .  by  4-0  per  cent,  to  3-1  per  cent 

Bakers'       .          .          .  ,  4-6  3-2 


CHAP,  vn]  FLOUR    MILLING  487 

The  fermentation  took  place  in  all  kinds  of  flour  equally  and  normally. 

The  baked  products  were  of  an  equal  structure.  The  brownish 
colouring  of  the  crust  was  a  little  deeper  for  the  bleached  flour.  The  bulks 
of  the  loaves  were  in  all  cases  good,  the  differences  fluctuating  within 
the  limits  of  inaccuracy  in  the  experiment.  On  the  average,  out  of  ten 
experiments,  there  was  obtained  to  100  gr.  of  flour  a  loaf  in  cubic  centi- 
metres : 

Unbleached.  Bleached. 

6  amp.  9  amp. 

Patent  flour     .      .      . .    .      ,458  453  456 

Bakers' flour   .      .      .      .      .   449  450  458 

The  numbers  received  in  practical  experiments  do  not  materially 
differ  from  them,  viz.  : 

Patent  flour    .     >      .      .      .   451  450  435 

Bakers' flour  .      ."     <      .      .   439  469  462 

Thus  it  appears  that  the  bleaching  of  flour  has  no  substantial  influence 
on  the  baking  process.  The  quantity  of  bread  obtained  proved  to  be  a 
little  less  for  bleached  flour  as  regards  weight,  there  being  no  difference 
in  its  bulk.  It  is  remarkable  that  the  bread  crumb  was  no  lighter  in 
colour  for  bleached  flour  than  for  unbleached.  In  respect  to  bread  baking 
the  advantages  of  bleaching  were,  consequently,  an  illusion. 

In  reviewing  the  results  of  all  the  experiments,  the  investigators 
arrived  at  the  conclusion  that  flour  bleaching  is  of  no  consequence  on 
principle. 

With  regard  to  baking,  the  bleaching  after  Alsop's,  Simon's  methods, 
and  others  similar  to  them  deserve  no  attention.  This  general  inference 
may  be  made  seeing  that  the  flour  used  for  the  experiments  was  of  ex- 
treme types.  The  flour  undergoes  no  modification,  neither  in  its  consis- 
tency nor  in  its  baking  qualities.  Therefore  the  improvement  in  the 
quality  of  the  flour  which  was  observed  (or,  at  least  was  asserted  to  have 
been  observed)  by  the  inventors  of  the  apparatus  must  be  denied.  How- 
ever, the  investigators  point  out  that  they  never  once  observed  any 
deterioration  in  the  flour  as  a  nutritive  substance. 

At  the  second  International  Pure  Food  Congress,  which  took  place  in 
Paris  in  October  18-24,  1909,  .as  regards  the  bleaching  of  flour  and 
middlings,  by  the  majority  of  votes  it  was  decided  to  allow  the  bleach- 
ing of  flour  by  means  of  nitrogen  oxides  on  condition  that  the  sacks  are 
stamped  with  a  special  mark.  No  injurious  consequences  to  the  health 
from  such  bleaching  were  discovered  by  the  Paris  Congress. 

The  bleaching  of  semolina,  on  the  contrary,  was  acknowledged  to  be 


4SS  M/)ttR   MILLING  [CHAP,  vn 

inadmissible,  since  it  would  allow  the  adulteration  of  hard  wheat  mid- 
dlings bleached  by  nature  itself  with  the  aid  of  white  rice  middlings. 

That  Congress  gave  utterance  to  what  the  investigators  were  already 
demanding  in  the  interests  of  custom  taxation,  namely  the  establishing 
of  standards  of  bleached  flour. 

But  on  the  other  hand,  in  the  United  States,  where  the  chemists,  E.  F. 
Ladd  and  K.  E.  Stallings  (North  Dakota),  are  stubborn  antagonists  of 
bleaching,  in  several  of  the  States  bleaching  is  considered  to  be  an 
adulteration  of  flour  injurious  to  health,  and  is  forbidden  by  law. 


CHAPTER   VIII 

MILLING   DIAGRAMS 

I 

CLASSIFICATION  OF  MILLING  SYSTEMS 

IN  the  preceding  chapters,  where  we  had  to  speak  of  the  reduction  of 
grain  in  connection  with  the  character  of  operation  of  the  machines,  we 
mentioned  in  brief  outlines  the  different  milling  systems.  Now  we  have 
to  give  a  definite  and  accurate  classification  of  the  various  milling  systems 
met  with  in  practice,  otherwise  it  will  be  difficult  to  make  out  the  innu- 
merable varieties  of  milling  schemes  proceeding  from  the  quality  of  grain, 
local  conditions  of  production,  and  the  demands  made  by  the  local, 
district,  and  world  markets. 

From  the  remotest  time  up  to  the  end  of  the  sixteenth  century  the 
technics  of  flour  milling  knew  only  one  method  of  reducing  the  grain, 
the  essence  of  which  consisted  in  that  the  grain  was  passed  but  once 
through  the  milling  machine  and  was  reduced  together  with  the  integu- 
ments. In  the  end  of  the  sixteeenth  century  there  was  invented  in  France 
another  method  of  milling,  ascribed  to  the  miller  Pigeaud.  That  method 
was  kept  in  secret  by  the  French  a  long  time,  until  in  1760  Bouquet,  a 
well-known  miller  in  Lyons,  published  it  under  the  name  of  "Mouture 
a  la  lyonnaise,"  having  perfected  the  old  French  method  of  milling  of 
the  end  of  the  sixteenth  century.  In  the  more  recent  French  literature 
that  milling  system  is  called  "  Mouture  economique."  The  essence  of 
that  system  lay  in  the  fact  that  the  grain  was  reduced  not  by  one  passage 
but  by  several.  When  letting  the  stock  pass  three  or  four  times  in  be- 
tween the  millstones,  the  upper  stone,  the  runner,  was  set  high  over  the 
lower  one,  and  gradually  the  distance  between  them  was  reduced  to  the 
normal  necessary  for  fine  grinding.  The  product  obtained  after  a  passage 
through  the  first  millstone  with  the  runner  set  high  was  bolted  on  a  reel- 
separator  and  gave  flour  as  throughs,  while  the  overtails  containing  the 
large  particles  of  grain  was  fed  to  the  second  stone,  the  grinding  and  the 
bolting  being  repeated  until  the  tails  from  the  last  reel-separator  consisted 

489 


490  FLOUR   MILLING  [CHAP,  viu 

of  bran.  Owing  to  such  a  method  of  milling,  a  considerable  part  of  the 
bran  was  not  admixed  to  the  flour,  and  the  flour  obtained  was  whiter. 

That  method  of  milling  began  to  spread  rapidly  in  Europe  and 
America  under  the  name  of  repeated,  high  or  reduction  system.  But  in 
Austria-Hungary,  where  the  dry  and  hard  wheat  has  brittle  coverings, 
that  method  gave  no  good  results,  as  the  integuments  were  reduced 
together  with  the  starchy  part  of  the  grain,  and  imparted  a  darker  colour- 
ing to  the  flour.  With  the  invention  of  the  purifier  by  the  Hungarian 
Paur  the  repeated  milling  was  enriched  by  one  very  important  stage  in 
the  milling  process — the  freeing  of  middlings  of  the  offals,  which 
brought  a  new  improving  alteration  into  the  milling  process. 

Thus  the  historical  course  of  development  of  grain  milling  and  its 
present  state  defines  two  methods  of  grinding  : 

1.  Plain  grinding. 

2.  Repeated  grinding. 

The  substance  of  these  methods  is  perfectly  clear  from  the  preceding. 
But  milling  practice  demands  a  complication  of  the  plain  milling 
towards  the  repeated  milling,  not  realising,  however,  fully  the  principle 
of  modern  high  milling  on  the  one  hand,  and  on  the  other,  often  simplifies 
the  high  milling,  without  bringing  it  up  to  the  complicated  system. 

German  flour  milling  technics  have  established  three  types  of 
milling  : 

I.  Flachmiihlerei — low  or  plain  grinding. 
II.  Halbhochmiihlerei — semi-high  grinding. 
III.  Hochmiihlerei — high  grinding. 

It  must  be  remarked,  however,  that  the  most  learned  Austrian 
scientist,  Professor  Kick,  foUows  the  first  classification,  i.e.  he  divides 
the  milling  in  two  groups,  plain  and  high,  regarding  the  semi-high 
milling  as  high  with  a  reduced  number  of  breaks. 

In  our  further  studies  of  milling  we  shall  keep  to  the  classification 
established  by  practice  and  defined  by  the  substance  of  the  process 
itself.  For  this  reason  we  offer  the  following  two  types  of  milling  systems  : 

1.  Plain  (low)  grinding. 
II.  High  grinding. 

The  essence  of  the  plain  milling  system  for  wheat  is  defined  not  by 
the  number  of  passages  of  the  product  through  the  grinding  machines, 
bat  by  the  purpose  of  these  passages.  The  object  of  each  passage  through 
the  grinding  machine  in  plain  milling,  is  to  obtain  flour  immediately  as 
the  chief  product.  The  total  number  of  passages  may  fluctuate  between 
one  and  five.  The  absence  of  purifiers  must  be  regarded  as  a  characteristic 


CHAP,  vm.]  FLOUR  MILLING  491 

feature  of  plain  wheat  grinding,  for  the  middlings  and  dunst  obtained 
are  not  graded  according  to  quality,  but  subjected  to  a  further  immediate 
reduction  to  obtain  a  greater  or  smaller  amount  of  flour. 

High  grinding  gives  us  three  separate  stages  in  the  process  of  reduc- 
tion. The  problem  of  the  first  stage  is  to  obtain  semolina,  middlings, 
and  dunst  with  the  least  possible  quantity  of  flour,  which  is  undesirable 
here,  because  it  becomes  dirtied  with  triturated  bran.  That  part  of  the 
process  is  called,  as  we  already  know,  break  (rebreak  must  also  be  included 
in  it).  In  the  second  stage  the  cleaned  semolina  undergoes  further  re- 
duction, which  may  be  named  rebreak  (in  Russia  that  process  is  called 
the  polishing  of  middlings).  The  object  of  this  part  of  high  grinding  is 
not  so  much  the  production  of  flour  as  the  reduction  of  semolina  to 
middlings  for  further  grading  according  to  quality.  Finally,  the  third 
stage  of  high  grinding  is  the  reduction  of  middlings  and  dunst  and 
the  cleaning  up  of  the  offals. 

We  must  regard  as  a  characteristic  peculiarity  of  high  grinding  the 
grading  of  middlings  and  dunst  according  to  quality,  and  consequently 
the  cycle  of  machinery  must  necessarily  include  a  purifier. 

The  characteristic  of  high  grinding  we  have  just  given  was  evolved 
by  Hungarian  flour  millers,  who  have  mostly  to  do  with  hard  wheats. 
That  system  has  been  accepted  partly  in  Germany  and  Russia.  In 
France,  England,  and  America  the  Hungarian  system  is  simplified  in  so 
far  that  the  number  of  breaks  in  it  is  seldom  more  than  five,  the  rebreak 
of  middlings  is  absent,  but  the  purifiers  are  always  included.  The  simpli- 
fied Hungarian  high  system  is  called  by  the  Germans  semi-high  (Halb- 
hochmuhlerei). 

High  rye  milling  differs  according  to  the  universally  accepted  plans 
from  wheat  milling,  in  that  the  grading  of  middlings  according  to  quality 
is  always  absent,  i.e.  the  cycle  of  machinery  contains  no  purifiers.  We 
shall  become  acquainted  with  this  system  of  milling  more  in  detail  below, 
and  turn  now  to  the  milling  diagrams. 

II 
PLAIN  GRINDING 

Single  Passage  Milling. — This  system  is  known  under  the  appellation 
of  peasant  grinding  in  Russia,  and  the  French  have  a  characteristic  name 
for  it  :  mouture  pour  le  pauvre  (milling  for  the  poor).  The  grain  is  passed 
through  the  stone  of  the  roller  mill  once  and  is  ground  to  flour  together 
with  the  offals.  In  this  manner,  the  system  yields  100  per  cent,  of 


492  FLOUR   MILLING  [CHAP,  viri 

flour.  The  bolting  away  of  the  unreduced  offals  is  done  by  hand  sieves 
before  baking  if  the  bran  is  too  large,  which  happens  when  the  grain 
is  not  perfectly  dry, 

The  Single  Passage  Sifted  Milling  differs  from  the  preceding  in  that  the 
bran  is  sifted  away  in  the  mill  by  means  of  a  reel  or  sifter.  In  the 
latter  case  the  mill  is  generally  constructed  for  improved  plain  milling, 
which  can  yield  two  or  three  kinds  of  flour,  but  in  dependence  on  the 
demand  for  the  peasant -sifted  flour  can  produce  this  flour  after  one  single 
passage.  The  single  passage  bolted  milling  yields  85  to  95  per  cent,  of  flour. 

Single  Passage  Intense  Milling. — The  aim  of  this  system  is  the 
reduction  to  flour  not  only  of  the  grain  kernel,  but  of  its  integuments  too. 
After  reduction  the  product  runs  to  the  bolting  machine,  which  yields 
flour  as  throughs  and  tails  over  bran.  The  bran  goes  to  the  same  sole 
milling  machine  which  receives  the  grain.  Thus  we  have  a  locked  cycle 
for  the  flow  of  the  bran,  which  results  in  the  bran  being  reduced  to  particles 
of  flour,  and  the  whole  100  per  cent,  of  flour  is  obtained  from  the  grain. 

Improved  Plain  Milling. — The  purpose  of  this  system  is  to  extract 
all  the  flour  particles  as  far  as  possible  from  the  grain,  and  to  separate 
away  the  offals  containing  no  flour.  The  number  of  reductions  in  this 
system  is  from  two  to  five,  the  product  after  each  reduction  machine 
passing  to  the  bolter. 

The  general  diagram  of  the  improved  plain  milling  system  is  this  : 

First  Reduction. 

^ ^ 

Flour  No.  1.  Dunst.  Middlings.  Hulls. 

Reduction  of  Middlings. 


Flour 
Nos.  2  & 

\ 

Dunst. 
3. 

1 

Cleaning  up. 

deduction 
i 

of  Dunst. 

I                          1 
Dark  Flour.     Coarse  and  Medium 
Bran. 

1 

Flour  Nos.  1  &  2.  Dark  Dunst. 

I 
Reduction  of  Dunst. 

* 

I 


Dark  Flour.  Fine  Offals  (blue  product). 

We  can  see  in  this  plan  that  each  reduction  system  yields  a  gradually 
deteriorating  flour,  dunst,  middlings  and  offals.  The  flour  deteriorates 
the  more  quickly,  the  less  the  number  is  of  reduction  systems. 


CHAP.   VIII] 


FLOUR    MILLING 


493 


It  has  already  been  mentioned  that  an  improved  plain  system  con- 
sists of  two  to  five  and  seldom  six  reductions.  With  two  reductions, 
generally  up  to  70  per  cent,  of  flour  is  obtained  from  the  first,  and  up  to 
15  per  cent,  from  the  second.  85  per  cent,  should  be  regarded  as  the 
limit  of  flour  yield  for  the  improved  plain  system ;  a  certain  percentage 
of  yields  for  each  reduction  may  be  at  the  same  time  taken,  to  calculate 
the  milling  machines.  In  the  case  given,  with  two  reductions,  the  first 
one  yields  70  per  cent,  of  flour  directly.  The  second  reduction  system 

30 
receives  the  remnant  of  the  product,  i.e.  ----.     If  we  take  50  per  cent,  of 

100 

flour  from  it,  we  obtain  =15  per  cent.     Thus  15  per  cent,  will  be 

100 

discharged  as  bran.     20  per  cent,  of  flour  might  be  taken  from  the  second 
reduction,  but  then  the  flour  would  be  too  dark. 

As  to  the  quantity  of  intermediate  products  on  the  improved  plain 
system  with  three  or  more  reductions,  modern  practice  offers  little 
definite  material.  In  that  case  much  depends  on  the  way  the  miller 
performs  the  reduction.  Still  we  must  append  the  data  of  a  German 
specialist,  Wingert,  for  three  and  six  reduction  systems  (Tables  LI 
and  LII). 

TABLE    LI 


Reactions.                   Product  Reduced. 

Fed  in 
100 
Per 
Cent 

Yielded  in  100  Per  Cent. 

Flour. 

Middlings 
and  Dunst. 

Bran. 

Blue  Flour. 

1          Cleaned  grain 
2         Middlings  and  dunst 
3         Middlings  and  dunst 

100 
30 
10 

50 
20 
10-7 

30 
10 

12             6 

Total  quantity  in  100  per  cent. 

140 

77-80 

40 

12 

6 

TABLE    LII 


1          Cleaned  grain       .      ; 

100 

35 

50 

15 

.. 

2         Middlings  and  dunst 

50 

25 

25 

.  . 

3  and  4     Dunst        .... 

25 

10 

15 

.  . 

5         Dunst        .      ...-•  .      . 
6         Bran    .      .      .      .      : 

15 
15 

r« 

V- 

24 

Total  quantity  in  100  per  cent. 

205 

76 

90 

15 

24 

494 


FLOUR   MILLING 


[CHAP,  vin 

Let  us  now  proceed  to  examine  several  typical  diagrams  of  the  im- 
proved plain  milling  system. 

Ill 
DIAGRAMS  OF  IMPROVED  PLAIN  MILLING  SYSTEMS 

The  improved  plain  milling  system  has  lately  begun  to  gain  a  wide 
local  market.  That  system  showed  particularly  rapid  development 

after  the  roller  mills  were  adopted.  The 
number  of  flour  grades  obtained  with  this 
system  is  generally  from  one  to  three,  and 
sometimes  up  to  five. 

Let  us  examine  several  typical  diagrams 
of  the  plain  roller  milling  system. 

Fig.  497  gives  a  diagram  of  the  plant 
for  a  mill  of  100  to  130  sacks  capacity 
per  24  hours. 

The  grain  is  deposited  in  the  storing 
bin,  whence  the  elevator  carries  it  to  the 
magnet,  which  detains  the  iron  extraneous 
matter.  From  the  magnet  apparatus,  the 
grain  flows  in  a  broad  sheet  to  the 
aspirator  (separator)  with  a  sieve  and 
manifold  fanning.  On  the  sieve  the  grain 
is  freed  of  the  large  impurities  :  straw, 
barley,  wild  oats,  maize,  &c.  On  the 
separator  likewise  are  partly  sorted  away 
the  small  impurities  :  cockle,  small  and 
broken  grain,  and  the  dirt  adhering  to  the 
stock. 

The  diameter  of  the  meshes  on  the 
aspirator  sieves  is  4  to  5|  mm.  the  large, 
and  2  mm.  the  small. 

After  the  aspirator  the  grain  goes  to  the 
cockle  cylinder  (trieur),  where  the  grain 
is  freed  of  cockle,  pease,  broken  and  small 
grains,  and  other  analogous  impurities. 

From  the  cockle  cylinder  the  grain  is 
directed  to  the  horizontal  emery  scourer 
with  triple  aspiration,  where  the  germ,  beard,  part  of  the  bran  coatings, 
and  dust  lying  in  the  crease  are  removed, 


FIG.  497. 

2c— Flour,  2nd  grade.        M— Flour  dust. 
Ic— Flour,  1st  grade.          p — Corrugations. 
A'-Cockle.  Kp— Bran. 

TT— Dust.  Me— Sharps. 

c—  Offals. 


CHAP,  vm]  FLOUR    MILLING  496 

From  the  emery  machine  the  grain  is  carried  by  the  elevator  to  be 
dampened,  and  then  to  the  bin  to  be  tempered  for  about  one  to  four  hours 
according  to  the  dampness  of  ^  the  grain.  Sometimes  dry  grain  (without 
any  dampening)  goes  directly  to  be  milled. 

The  dust  from  the  grain-cleaning  machines  passes  to  the  dust  chamber 
and  thence  into  sacks. 

The  reduction  is  performed  by  two  pairs  of  rolls.  But  since  it  is  diffi- 
cult to  reduce  the  grain  in  two  passages  (much  power  is  uselessly  spent ; 
a  whiter  and  a  finer  flour  cannot  be  obtained,  the  bran  discharged  is  very 
rich),  an  accessory  breaking  down  passage  is  introduced  into  the  scheme. 

The  length  of  the  break  rolls  is  taken  approximately  one-third  less 
than  the  reduction  rolls. 

Length  of  the  break  rolls  is        .  .  .  .  500  mm. 

Diameter         v         .          t          .  .  .  .  250  mm. 

Number  of  corrugations  to  an  inch  .  ,  16 

Differential  velocity  of  the  rolls  .  .  .  1  :  1  or  1  :  3. 

If  the  differential  velocity  of  the  break  rolls  is  1  :  1,  the  grain  will  be 
broken  in  halves  ;  the  differential  velocity  being  1:3,  the  grain  is  divided 
into  several  parts. 

From  the  break  mill  the  grain  passes  directly  to  -the  first  reduction 
pair. 

Length  of  rolls  in  the  first  reduction  mill     .          .     800  mm. 
Diameter         .          .          .          .          .         ."         .     300  mm. 

Number  of  corrugations  to  an  inch     .         ..          '.     24 
Differential  velocity  of  rolls       .       ..-..          .          .     1:3. 

From  the  first  reduction  mill  the  whole  of  the  mixed  product  is  carried 
by  an  automatic  elevator  to  the  reel-separator,  which  is  clothed  with 
silks  Nos.  VII,  VIII,  IX,  and  X. 

The  tails  of  the  reel-separator  goes  to  the  second  reduction  mill, 
and  the  throughs  yield  high  grade  flour. 

Number  of  revolutions  of  the  reel  .          /         .25 
Diameter  of  the  reel-cylinder     .  .          .     900  mm. 

Bolting  cloths ....  .3 

Breadth  of  cloths     ...  .     33 -25  inches. 

From  the  second  reduction  mill  the  whole  mixture  passes  to  the 
4-cloth  reel-separator,  which  is  clothed  in  metal  sieves  and  has  the  follow- 
ing numbers  :  46,  44,  42,  and  40. 

The  tails  from  this  reel-separator  is  large  bran,  while  the  throughs 
go  to  the  next  reel-separator  with  five  cloths,  and  the  numbers  of  silk 
are  VII,  VIII,  IX,  X,  and  III, 


496 


FLOUR    MILLING 


[CHAP,  vni 


The  tails  of  that  reel-separator  are  fine  bran,  and  the  throughs 
yield  flour  of  the  second  grade  and  dunst,  which  goes  to  the  mill. 

If  it  is  desired  to  give  a  better  finish  to  the  goods  of  the  second  grade 
the  dunst  is  sacked  off. 


Length  of  rolls  of  the  second  reduction  mill 
Diameter 
Differential  velocity  of  the  rolls 
Number  of  corrugations  to  an  inch     . 
Number  of  revolutions  of  the  4-  and  5-cloth  reel- 
separators 
Diameter  of  the  reel-cylinder     . 

Both  the  reduction  and  the  break  mill  are  exhausted. 


800  mm. 
300  mm. 
1  :3 

28 

28 

900  mm. 


FIG.  498. 

The  ordinary  type  of  the  popular  improved  plain  milling  system, 
especially  in  the  south  of  Russia,  has  the  following  form  : 

Grain  Cleaning. — An  aspirator  or  separator  with  a  sieve,  a  trieur 
(cylinder),  and  a  horizontal  scourer. 

Grain  Reduction. — Two  passages  through  corrugated  rolls  and  one 
passage  through  a  millstone.  After  the  roller  passages  the  product  is 
bolted  on  sifters  or  on  reels.  After  the  stone,  which  cleans  out  the 
bran,  the  bolting  yields  flour  of  the  last  grade  and  the  refuse  gives 
bran.  If  two  grades  of  flour  are  prepared,  the  product  is  yielded  as 
follows  :  first  grade  45  per  cent.,  second  grade  36-25  per  cent.,  bran 
17-5  per  cent.,  different  losses  1-25  per  cent.  If  desired  the  first  and 
second  grades  may  be  mixed  to  one  straight  grade. 

Fig.  498  illustrates  a  milling  diagram  with  four  passages.  The  grain- 
cleaning  department  of  such  a  mill  consists  of  the  following  machines : 
the  grain  goes  first  to  the  dust  reel-separator,  where  it  is  freed  of  heavy 
dust  and  small  extraneous  matter.  The  wire  cloth  used  for  small  impuri- 
ties and  dust  is  No.  16,  to  separate  the  large  impurities  from  the  grain  No.  5 


FLOUR    MILLING 


407 


CHAP.    Vlll] 

(to  an  inch).  From  the  reel-separator  the  grain  goes  to  the  trieur,  whence 
it  passes  to  the  magnet  apparatus.  From  the  magnet  apparatus  it  goes 
to  the  horizontal  emery  scourer.  From  the  scourer  into  two  bins, 
where  the  grain  is  tempered  for  five  or  six  hours.  Then  it  goes  to  the 
reduction  machines. 

Grain  Reduction. — The  reduction  is  performed  in  two  four-roller  mills. 
The  first  one  is  450x200  mm.  in  size,  the  second  700x300  mm.  The 
whole  reduction  process  is  ended  in  four  passages.  The  first  break 
gives  dark  flour  (blue  flour)  and  coarse  middlings,  which  are  bolted  on  a 
3-metre  reel-separator.  The  refuse  goes  to  the  second  break,  which  is 
bolted  on  a  4-metre  reel-separator.  The  flour  obtained  is  fairly  white, 
and  the  middlings  are  medium  sized  and  mix  with  the  middlings  from  the 
first  break,  and  together  with  them  run  to  the  smooth  rolls,  where  both 


FIG.  499. 

are  reduced,  and  give  white  flour  first  grade,  and  overtails,  the  so-called 
flat  product,  which  mixes  with  the  tails  from  the  second  break  and  goes 
to  the  fourth  passage.  Here  the  flat  product  and  the  tails  from  the  second 
passage  undergo  a  final  reduction,  and  are  then  bolted  on  a  4-metre  reel- 
separator,  where  the  flour  obtained  is  better  than  the  one  from  the  first 
passage  and  darker  than  that  from  the  second.  Since  the  flour  goes  to 
a  common  conveyor,  the  grades  may  be  combined  at  pleasure  ;  the  first 
may  be  obtained  separately,  I,  II,  III,  and  IV,  &c.  Naturally,  instead 
of  reel-separators  sifters  may  be  employed.  That  mill  can  grind  up 
to  500  bushels  of  wheat  per  day  (24  hours)  on  this  plan. 

Fig.  499  shows  a  diagram  of  cleaning  and  reduction  with  five 
reduction  passages. 

Grain  Cleaning. — The  inexpensive  cleaning  department  of  the  mill 
consists  of  an  aspirator,  a  trieur,  a  Seek  scouring  machine  with  a 

scouring  sieve,  Luther's   emery  scourer,  a  brush  machine,  and  a  clean 

2i 


498  FLOUR    MILLING  [CHAP,  vm 

reel-separator.  From  the  storing  bin  the  grain  is  fed  to  the  aspirator 
with  one  or  two  sieves,  where  it  is  freed  of  large  and  fine  impurities, 
such  as  straws,  cobs,  clods  of  dirt,  &c.  The  fan  in  the  meanwhile 
carries  away  the  dust,  which  is  of  very  little  value,  to  the  cyclone  or  the 
filters.  After  that  the  grain  passes  to  the  trieur,  where  the  cockle,  pease, 
&c.,  are  separated  away. 

In  this  manner  the  grain,  freed  of  all  foreign  matter,  undergoes 
further  treatment.  The  beard  and  the  germ  coats  are  broken  off,  the  grain 
is  polished,  and  then  passes  to  the  reel-separator  ;  from  the  reel-separator 
to  the  brush,  where  the  grain  is  subjected  to  a  final  polishing,  and  at  the 
same  time  the  dust  brushed  out  of  the  creases.  The  pure  grain  is  damped 
and  then,  by  means  of  the  conveyor,  more  or  less  satisfactorily  stirred 
and  carried  into  bins  for  tempering.  The  grain  thus  prepared  is  then 
milled. 

The  Milling  Department  (Fig.  499)  consists  of  three  four-roller  mills, 
a  two-box  sifter  with  four  divisions,  and  a  reel-separator.  The  first  mill 
is  32  x  12  in.,  the  second  32  x  14  in.,  the  third  20  x  10  in.  The  second 
mill  has  one  pair  of  smooth  rolls  which  reduce  fine  middlings.  The 
bolting  machines  may  also  be  set  in  the  following  order  :  one  sifter  for 
three  products  and  the  second  sifter  for  two  products. 

The  number  of  grooves  on  the  first  pair  of  rolls  in  the  first  mill  is  16 
to  an  inch,  on  the  second  pair  of  the  first  mill  18.  on  the  fourth  pair  of  the 
second  mill  22,  and  in  the  third  mill  both  pairs  of  rolls  have  26  grooves. 

The  order  of  milling  is  the  following.  Before  the  first  passage  the 
grain  runs  over  the  magnet  apparatus.  In  the  first  passage  the  grain  is 
broken  down,  and  the  product  of  grinding  goes  to  the  first  division  of 
the  sifter.  The  larger  break  chop  and  large  semolina,  and  the  tails  of 
the  bottom  tray  undergo  a  second  passage.  The  product  obtained  passes 
to  the  second  division  of  the  sifter.  The  throughs  from  the  bottom  trays 
of  the  first  two  systems,  fine  semolina,  are  fed  to  the  smooth  rolls  ///. 
The  product  ground  is  bolted  in  the  third  division  of  the  sifter.  The 
larger  chop  and  rebreak,  and  the  bottom  tails  of  the  second  divi- 
sion, the  tails  of  the  top  sieves,  and  the  bottom  tails  of  the  third  division, 
go  to  the  fourth  pair  of  corrugated  rolls.  The  product  received  from 
the  fourth  pair  runs  to  the  fourth  division  of  the  sifter,  where  from  the  first 
two  trays  cleaned  large  bran  is  obtained.  The  product  of  the  next  two 
trays  and  the  bottom  tails,  dark  dunst,  pass  to  the  fifth  pair  of  rolls. 
The  product  from  the  fifth  rolls  is  fed  to  the  reel-separator,  whence  fine 
bran  and  dark  dunst  are  discharged  as  tails.  If  desired  the  dark  dunst 
can  be  delivered  separately.  Then  the  last  cloth  in  the  reel-separator 


CHAP,  vm]  FLOUR    MILLING  499 

should  be  for  dunst,  i.e.  No.  5.  Both  the  order  of  milling,  as  well  as  the 
products  obtained,  are  clearly  seen  in  the  diagram.  The  whole  of  the 
flour  is  received  by  the  conveyor,  where  it  blends  into  one  grade  named 
sifted  flour.  In  case  of  need  it  may  be  separated  into  grades.  It  is  evi- 
dent that  the  flour  from  the  smooth  rolls  of  the  third  system  is  the  best. 
The  next  in  quality  is  the  flour  from  the  second  system.  The  darker 
grades  are  obtained  from  the  first,  fourth,  and  fifth  systems.  When 
milling  soft  kinds  of  wheat  in  the  place  of  Nos.  48  in  the  first  and  second 
divisions  of  the  sifter,  Nos.  42  should  be  set,  keeping  the  grinding  in  the 
first  and  second  systems  as  high  as  possible.  Then  in  all  the  divisions 
of  the  sifter  flour  silks  coarser  by  one  number  must  be  placed. 

This  milling  system  is  in  vogue  in  the  region  of  the  Northern 
Caucasus,  and  mills  of  that  type  work  for  peasants,  who  bring  the  grain 
from  quite  remote  parts.  Owing  to  the  latter  circumstance,  the  possi- 
bility of  correctly  tempering  the  grain  is  not  everywhere  possible.  This 
is  explained  by  the  fact  that  in  some  places  the  peasants,  on  bringing  the 
grain,  pour  it  into  the  pit  for  immediate  milling. 

Under  such  conditions  the  dampening  of  the  grain  is  greatly  hindered. 
To  avoid  undesirable  consequences  in  that  respect,  there  have  to  be 
arranged  five  or  six  bins  of  25  to  35  bushels  capacity  each,  and  the  milling 
operation  performed  in  such  a  manner,  that  when  one  bin  is  emptied,  the 
grist  should  be  directed  from  the  next  one,  and  the  empty  bin  filled  with 
the  grain  cleaned  in  the  scourer.  Then,  while  the  grist  is  flowing  out  of 
the  first  bin,  the  grain  in  the  fifth  or  sixth  bin,  i.e.  belonging  to  the  cus- 
tomer standing  in  the  fifth  or  sixth  place,  has  a  certain  possibility  of  being 
tempered.  In  other  parts,  where  the  peasantry  leave  the  grain  and  come 
to  fetch  the  flour  in  two  or  three  days'  time,  it  is  quite  possible  to  temper 
the  grain  correctly.  Still  better  is  this  operation  arranged  in  localities 
where  the  peasants  get  the  quantity  of  flour  according  to  the  weight  of 
their  grain. 

Now,  the  question  arises,  How  are  the  interests  of  the  mill  customers 
who  have  grain  of  different  qualities,  in  respect  to  its  impurity  as  well  as 
specific  weight,  to  be  reconciled  ? 

To  answer  this  case  practice  has  evolved  the  following  rules. 

For  grain  containing  a  fairly  large  amount  of  impurities  the  loss  in 
the  product  escaped  with  the  air  and  in  grain  cleaning  allowed  is  from 
3  to  5  Ib.  per  36  lb.,  and  not  over  1  to  1J  Ib.  for  grain  of  higher  purity. 

The  regulation  concerning  flour  is  similar  to  it.  Owing  to  such 
regulations  it  is  possible  to  mill  the  grain  of  different  customers  together. 

Of    course,   a    lot   ought   not  to  have  such   wheat    admixed   to   it 


500  FLOUR    MILLING  [CHAP,  vm 

containing  any  proportion  of  rye,  even  if  the  quantity  of  admixture 
should  be  small,  because  the  flour  assumes  a  darker  colouring  in  conse- 
quence. 

Under  such  circumstances  it  is  possible  to  treat  all  the  grain  together 
and  temper  it  some  ten  or  twelve  hours  if  it  is  of  a  hard  kind,  and  four  or 
five  if  softer. 

It  is  very 'desirable  that  the  grain  cleaning  should  be  performed  in 
two  scouring  passages,  it  being  necessary  to  dampen  the  grain  before  it 
goes  to  the  second  scouring  passage.  In  such  a  grain-cleaning  process  the 
first  scouring  passage  frees  the  grain  of  the  dust  and  dirt.  After  damp- 
ing the  grain  is  tempered,  and  then  undergoes  the  second  scouring  passage. 

But  since  grain  cleaning  of  that  kind  at  the  farm  mills  is  compara- 
tively expensive,  it  is  difficult  to  expect  it  to  spread,  though  we  must 
remark  that  good  flour  repays  the  extra  expenses. 

The  mills  described  grind  Kubanka  with  a  10  or  20  per  cent,  admixture 
of  winter  wheat. 

In  ending  the  review  of  the  improved  plain  milling  system,  the  fact 
should  be  noted  that  with  this  system  it  is  not  difficult  to  obtain  good 
flour  from  soft  wheat  covered  with  elastic  bran  coats,  which  do  not  break  up 
so  much,  and  leave  the  flour  undirtied.  The  best  grades  of  flour  prepared 
from  hard  wheats,  on  the  other  hand,  become  dirty  owing  to  the  offal  being 
ground.  For  this  reason  the  milling  has  to  be  performed  cautiously,  the 
dry  grain  being  damped  and  the  number  of  passages  increased. 


IV 

HIGH  GRINDING 

The  high,  repeated,  or  gradual  reduction  process  has  already  been 
characterised  in  brief  outline.  We  shall  now  study  it  more  minutely. 

To  extract  the  whole  of  the  mealy  part  out  of  the  grain  and  separate 
away  the  integuments,  having  removed  as  far  as  possible  all  mealy  parts, 
is  the  purpose  of  high  grinding.  This  is  attained  in  a  certain  degree  by 
the  break  and  rebreak  process,  the  aim  of  which  is  to  break  the  grain 
down  to  middlings  and  dunst,  to  separate  from  them  the  particles  con- 
taining no  offals,  and  lastly,  extract  out  of  the  particles  of  integument  the 
remaining  particles  of  meal. 

As  regards  the  character  of  reduction,  high  grinding  may  be  divided 
into  four  separate  categories.  In  the  first  must  be  placed  the  breaking 
of  the  berry  down  the  crease,  which  allows  of  the  removal  of  dust 


CHAP,  vin]  FLOUR   MILLING  501 

settled  in  the  crease  from  the  halves,  and  otherwise  inextractable  in  the 
cleaning  process.  The  French  call  this  passage  "  preliminary  break  " 
(lavant  broyage),  the  Germans  Hochschrot.  In  the  second  category 
are  a  series  of  passages  in  which  the  halves  of  grain  are  consecutively 
ground  to  middlings  and  dunst  ("  break  propar."  broyage  proprement  dit) 
of  a  better  quality. 

In  the  passages  of  the  third  category,  which  should  be  named  the 
"  completion  of  break  "  (complement  de  broyage),  middlings  and  dunst 
of  a  lower  quality  (soft)  are  produced.  Finally,  the  passages  of  the  fourth 
category  are  designed  to  clean  off  the  mealy  particles  from  the  bran  (curage 
des  sons). 

A  developed  rebreaking  process  in  which  there  are  at  least  three  pas- 
sages represents  the  three  last  categories  of  the  breaking  process,  or  with 
one  or  two  the  reduction  of  the  rebreak  middlings. 

The  breaking  and  rebreaking  process  has  to  be  so  performed  as  to 
produce  as  little  flour  as  possible,  because  it  cannot  be  freed  from  the  mealy 
particles  of  integument,  and  can  be  sent  only  to  the  worst  grades. 

The  number  of  breaks  varies  between  five  and  ten,  the  breaking  of 
the  grain  down  the  crease  included  ;  the  number  of  rebreaks,  between 
one  and  five.  The  harder  the  wheat  is  and  the  more  middlings  and  less 
break  flour  is  it  desirable  to  obtain,  the  greater  is  the  number  of  passages 
used. 

The  product  obtained  from  each  separate  passage  is  sorted  on 
bolting  machines,  and  gives  a  series  of  middlings  and  dunst  of  various  size 
and  quality.  Then  they  are  blended  according  to  size  and  quality 
(sharp  or  hard  and  soft),  and  subjected  to  grading  according  to  their 
quality  on  purifiers. 

When  the  middlings  and  dunst  are  freed  of  bran  and  graded 
according  to  size  and  quality,  the  process  of  reduction  commences.  That 
process  is  divided  into  two  parts.  First  the  middlings  are  broken  down 
finer.  That  part  of  reduction  is  analogous  to  the  rebreaking  process, 
and  ought  to  ba  named  the  rebreak  of  middlings  (polishing  of  semolina). 
The  sense  of  that  part  of  the  process  has  to  b?  explained.  However  well 
the  purifier  may  work,  we  shall  always  have  a  certain  percentage  of 
middlings  covered  with  offals.  It  is  impossible  to  extract  these  grains 
of  middlings,  but  by  breaking  them  down  on  porcelain  or  smooth  rolls, 
we  obtain  particles  of  these  middlings  covered  with  bran  coats  of  a  larger 
size  than  those  of  pure  starch.  Owing  to  that  we  have  the  possibility 
of  separating  the  branny  middlings  on  bolting  machines  in  a  second 
grading  according  to  quality. 


502  FLOUK   MILLING  [CHAP,  vni 

Consequently,  in  developed  high  grinding,  when  rebreaking  the 
middlings,  the  production  of  a  large  quantity  of  flour  should  likewise  be 
avoided. 

Finally,  when  the  middlings  and  dunst  are  completely  graded,  they 
are  reduced  to  flour  on  smooth  rolls. 

With  the  details  of  high  grinding  we  shall  become  acquainted  through 
the  various  milling  diagrams  ;  at  present  we  give  a  general  plan  of  high 
grinding. 

1.   The  Break  Process  (5  to  10  passages). 

I T 

Flour.        Dunst.        Middlings.  Rebreak  Semolina.  Large  Bran. 

2.  Rebreak  Process  (1  to  5  passages). 

Flour.        Dunst.         Middlings. < ^Medium  Bran. 


3.  Grading  according  to  Size. 

!  I 

Flour.  <-— 


4.  Grading  according  to  Quality. 

1  -v  --  ' 

Offals.     Dunst.     Middlings. 


CLEANING  THE  OFFALS.<  * 

1 
J>.  Rebreak 

of  Middlings  (2  to  5  passages  ); 

Fine  Offal.     Dark  Flour. 
6.  Reduction  of  Dunst.  •*- 

Flour 

Fine  Offal.          Flour,  including  highest  grades,  &c. 

We  shall  now  proceed  to  acquaint  ourselves  with  the  milling  diagrams 
designed  for  this  system. 

Hungarian  High  Grinding.— On  Fig.  500  we  see  the  diagram  of  Hun- 
garian high  grinding  for  a  mill  with  a  capacity  of  5000  bushels  of  wheat 
per  24  hours. 

The  grain-cleaning  diagram  includes  the  diagram  of  silo  cleaning 
with  a  passage  of  the  grain  through  a  zigzag  separator  and  its  distri- 
bution in  the  fourteen  silos  of  the  elevator.  From  the  silo  the  grain 
goes  through  the  grain-blending  apparatus  to  the  zigzag  separator  of  the 
grain-cleaning  department,  then  through  the  magnet  apparatus  and  a 
two-box  sifter  with  metal  sieves,  which  grades  the  grain  according  to  size. 
The  grain  graded  according  to  size  passes  to  two  groups  of  trieurs,  con- 
sisting of  cockle  cylinders,  barley  cylinders,  and  re-cylinders.  The 
product  received  from  the  trieurs  may  further  be  subjected  to  double 


CHAP.   Vlll] 


FLOUR    MILLING 


503 


Fio.  500. 


SLOtJR   MILLING  (CHAP,  viii 

cleaning  :  dry  and  wet.  In  cases  when  the  grain  is  not  too  dry  the 
washing  plant  is  missed.  The  grain  passes  consecutively  two  emery 
horizontal  scourers,  then  it  goes  to  the  floor  brush  machine  and  through 
the  scale  into  the  bins  for  further  treatment  in  roller  mills.  The  small 
and  large  grain  undergoes  scouring  on  parallel  separate  scourers  and 
brushes.  If  the  wheat  is  very  dry  and  hard  it  is  subjected  to  wet  scour- 
ing. Then  from  the  trieurs  the  grain  goes  directly  to  the  washing 
machine,  whence,  after  drying  and  tempering  in  bins,  it  is  taken  to  be 
scoured. 

The  cleaning  scheme  examined  here  is  far  from  perfect,  since  the 
sifting  away  of  heavy  offals  between  the  first  and  the  second  scouring 
passage  has  not  been  provided  for,  and  a  magnet  and  a  dampening 
apparatus  after  the  brush  machine  are  absent. 

The  milling  process  forms  three  groups  of  roller  passages,  and  the 
rebreak  (polishing)  of  middlings  and  reduction  of  middlings  and  dunst 
are  ended  by  the  millstones  for  scraping  out  blue  flour. 

The  first  break  system  consists  of  seven  breaking  passages  and  two 
rebreaking  passages.  We  must  note  that  the  Hochschrot  is  absent  here, 
and  the  whole  breaking  process  is  not  developed  to  its  utmost  limit. 
The  rebreak  (scratch)  rolls  treat  the  middlings  which  are  tailed  over  by  the 
purifier.  The  reduced  product  is  subjected  to  a  preliminary  grading  on  the 
first  group  of  sifters,  on  which  the  break  flour  is  separated  and  the  pre- 
liminary grading  of  middlings  and  dunst  according  to  size  is  performed. 
The  last  breaking  passage  cleans  the  bran  and  heavy  offals  of  the  puri- 
fiers which  sort  the  large  and  medium  semolina.  The  product  from  this 
passage  goes  first  to  the  reel-separator  which  gives  bran  as  tails,  while 
the  throughs  pass  to  the  sifter,  which  gives  dark  flour,  blue  flours  of 
medium  size,  and  dark  dunst  of  two  kinds.  The  blue  flours  go  to  be 
reduced  on  the  stones,  for  middlings  rebreak,  and  the  second  grade  of 
dunst  to  the  seventh  reduction. 

After  the  preliminary  grading  the  middlings  and  dunst  pass  to  the 
sifters,  which  sort  them  into  three  to  eight  grades  according  to  size.  Here 
the  breaking  and  rebreaking  processes  end.  The  product,  graded  accord- 
ing to  size,  runs  next  to  the  first  group  of  purifiers,  which  sort  it  according 
to  quality.  After  that  operation  the  product,  grouped  according  to  size, 
undergoes  a  process  we  name  middlings  rebreak.  The  middlings  rebreak 
performed  on  smooth  rolls  is  in  fact  a  process  analogous  to  the  break 
process.  For  this  reason  for  the  larger  middlings  we  have  here  a  system 
of  sifters  and  purifiers.  That  process  is,  of  course,  much  shorter  than  the 
breaking  process.  The  sifters  of  this  system  supply  us  with  flour,  dunst, 


I    trsd  — Erd     tsd 


506  FLOUR   MILLING  [CHAP,  vm 

and  middlings,  which  are  subjected  to  a  final  reduction  on  the  third 
reduction  system  of  smooth  rolls.  The  number  of  reduction  passages 
is  nine,  the  stone  for  cleaning  up  the  dark  dunst  included. 

German  High  Grinding— To  illustrate  a  typical  German  high  grind- 
ing system  at  the  Dresden  Exhibition  in  1911,  the  firm  of  Seek  Bros, 
exhibited  the  milling  diagram  shown  in  Fig.  501.  The  mill  grinds  about 
6000  bushels  of  wheat  per  day  (24  hours).  We  shall  pass  by  the 
diagram  of  the  silo  and  the  wheat-cleaning  system,  and  only  point  out  that 
grain  cleaning  in  the  mill  is  developed  considerably  better  than  in  the 
preceding  plan.  Here  the  wet  scouring  of  grain  with  a  dryer  and  without 
it  is  provided  for. 

The  mill  proper  is  arranged  after  the  same  scheme  that  is  used  in 
the  Hungarian  mill,  with  the  sole  difference  that  the  number  of  breaks 
in  this  case  is  limited  to  six,  the  number  of  rebreaking  passages  for 
middlings  is  reduced,  but  the  number  of  reductions  is  increased.  The 
bolting  machines  for  semolina  rebreak  are  centrifugals  and  sifters  in 
conjunction.  Besides  that,  to  obtain  the  final  product,  flour,  there  are 
centrifugal  redressers. 

The  two  diagrams  of  high  grinding  systems  examined  give  a  sufficient 
idea  of  the  standard  separate  stages  of  the  milling  process. 

Since  we  are  acquainted  with  a  general  outline  of  the  grading  of 
the  product  of  the  breaks,  a  more  detailed  plan  of  that  grading  should 
be  given. 

Let  us  take,  for  example,  the  third  break  (Fig.  502),  as  character- 
istic of  break  stock,  and  examine  the  process  of  grading  the  product 
obtained. 

The  product  of  the  third  break  passes  on  to  the  sifter  No.  1,  the  upper 
sieve  of  which  is  covered  with  a  metal  cloth  No.  18.  The  overtails  are 
break  stock  for  the  fourth  break.  The  next  sieve  is  likewise  covered  with 
a  metal  cloth  No.  22,  and  yields  the  rebreak  semolina.  Then  follow  two 
silk  flour  sieves  Nos.  10  and  11  ;  next  one  silk  sieve  No.  3,  for  separating 
middlings  from  the  dunst ;  and  finally,  one  silk  sieve  No.  9,  for  separating 
dunst  as  throughs  and  fine  middlings  as  tails.  Before  the  flour  sieve 
very  often  is  set  a  sieve  for  separating  the  large  semolina  (Nos.  32-38). 
The  mixed  middlings  of  the  tails  of  No.  3  go  to  the  sifter  No.  2,  which 
grades  them  into  eight  different  sizes,  and  hence  each  of  the  eight  grades 
passes  to  the  purifier  A  for  treating  the  semolina. 

All  the  first  runs  of  purified  stock  are  generally  mixed  together, 
but  each  size  may  be  collected  into  sacks  or  spouts  (if  automatic) 
separately,  if  desired.  The  same  may  be  said  of  the  second  runs. 


CHAP,  vm]  FLOUR   MILLING  507 

The  third  sizes  of  middlings  are  mixed  together,  &c.  The  offals  of  all 
the  eight  sections  of  the  purifier  are  likewise  run  together. 

The  throughs  of  the  last  sieve  (No.  52)  consist  of  dunst,  which  is 
directed  to  the  sitter  No.  3  for  dunst. 

The  dunst  from  the  break  sifter  (No.  1)  goes  to  the  dunst  sifter  No.  3 


—    ...    --- 

.1 

—  _^____ 

'-;  ;  ! 

_.!*_  

-*     1    '    1 

1     ,    '    1 

<<0 

II1 

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1         I    ' 

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l'11 

~———— 

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ILJL.'J!  jLliUt.-UJ.V.U 

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FIG.  502. 

which  grades  the  dunsts.  The  top  sieve  yields  flour.  Then  follow  six 
dunst  sieves  (Nos.  8,  7,  6,  5,  4,  and  3)  of  which  the  last,  No.  3,  tails  over 
middlings  which  are  directed  to  the  sifter  No.  2.  The  throughs  from  these 
six  sieves  go  to  the  purifier  B  yielding  the  first,  second,  and  third  cleaned 
dunst,  which  are  reduced  together  independently  of  the  size,  but  divided 
according  to  quality.  The  light  offals  constitute  a  finished  product. 


£08  FLOUR   MILLING  [CHAP,  vm 

The  quantities  of  middlings  yielded  with  a  well- arranged  high  grinding 
system  are  given  in  the  appended  table.  The  raw  material  here  is 
Hungarian  wheat,  weighing  8-1  klg.  a  litre. 

There  were  obtained  : 

Middlings  from  sieve  No.  24  .  .  .15  per  cent. 

„  No.  28  .  .  .',     12        ,. 

„         „  No.  32  .  .  .     11        „ 

„  No.  36  .  .  .     12        „ 

„         „  No.  40  9 

„  No.  44  .  .  .       5        „ 

„  No.  48  .  3        „ 

„  No.  52  .  .•      2        ,r 

69  per  cent. 

Dunst         .          .          .          .          .          .          .9-5  per  cent. 

Break  flour          .          .          .          .          .          .     6-0        „ 

Bran 14-0 

Losses         .          .          .          .          .          .  1-5        „ 

31  per  cent. 

In  a  similar  manner  are  obtained  the  middlings  and  dunst  of  the 
remaining  breaks,  ending  with  the  fifth  or  sixth  break. 

Now  there  remains  the  further  process  of  grading  the  middlings  to  be 
examined — their  sorting  for  reduction  to  flour. 

We  know  that  the  production  of  semolina  is  not  a  fundamental  purpose 
of  milling.  For  its  production,  in  America  for  instance,  there  are  special 
mills,  which  prepare  such  semolina  for  certain  kinds  of  biscuits.  In 
Russia  and  in  Europe  semolina  is  a  by-product  of  milling,  and  is  obtained 
directly  from  the  controlling  purifier. 

The  number  of  grades  of  cleaned  middlings  must  be  reckoned  as  not 
exceeding  four,  and  dunst  three.  In  the  rest  of  the  breaks  from  the 
sixth  to  the  eighth  (the  ninth  cleans  the  bran)  there  is  still  much  dunst 
produced,  as  well  as  a  small  quantity  of  poor  middlings  which  are  not 
worth  cleaning.  Therefore  they  are  reduced  to  the  lowest  grades  of  flour 
untreated  or  treated  very  slightly.  We  shall  not  speak  of  them  here, 
since  we  have  only  the  best  middlings  and  dunst  in  view. 

The  middlings  are  reduced  on  smooth  rolls,  avoiding  as  far  as  possible 
the  formation  of  flour,  to  dunst  and  then  to  flour. 

Further,  we  must  note  that  all  middlings  and  dunst  of  equal 
quality,  even  though  of  different  size,  are  blended  together,  from  the 
second  to  the  fifth  break.  Now  supposing  the  middlings  and  dunst 


FLOUR    MILLING 


509 


CHAP.    VIII] 

to  be  separated  and  then  graded  and  purified  as  in  the  diagram 
(Fig.  502),  the  following  diagram  (Fig.  503)  shows  the  further 
treatment  all  the  purified  middlings  and  dunst  receive. 


r— teS 


We  begin  with  the  coarser  purified  semolina  (in  the  diagram,  Fig.  503, 
middlings  I).  It  runs  to  the  rolls,  is  reduced  there,  and  then  sent  to 
the  sifter  No.  1.  The  flour  goes  to  the  sack  or  to  a  redresser. 


510  FLOUR   MILLING  [CHAP,  vm 

The  overtails  of  the  sifter  go  to  the  second  rolls,  to  which  the  second 
middlings  are  likewise  directed.  The  first  middlings  have  become 
equal  to  the  second  in  size  and  quality  after  the  reduction.  The  best 
dunst  from  sifter  No.  1  goes  to  the  first  reduction  mill  (1),  where 
it  is  finally  ground  to  flour.  The  latter  is  produced  in  large  quantities, 
and  after  bolting  is  sacked  off  or  also  conveyed  to  the  redressing  sifter 
and  then  into  a  bin  (this  is  not  given  in  the  diagram,  our  aim  being  to 
illustrate  the  treatment  received  by  the  middlings). 

The  tails  of  the  first  and  the  last  sieve  of  sifter  No.  1  consist  of  rich, 
uncleaned  offal,  which,  on  being  blended  with  like  particles  from  other 
sifters,  is  cleaned  up  separately,  as  will  be  shown  presently.  The  remaining 
dunst  passes  to  the  second  reduction  mill  (2),  where  the  same  process  as  in 
the  first  takes  place. 

That  which  remains  unreduced  of  the  dunst  (the  throughs  from 
the  last  sieve  of  sifter  No.  II)  goes  to  the  mill  (3)  of  the  second 
middlings. 

The  second  middlings,  together  with  the  tails  of  the  first,  are  ground 
on  the  second  mill.  The  tails  of  sifter  No.  2  pass  to  the  third  mill, 
where,  on  being  mixed  with  the  third  middlings,  it  undergoes  the  same 
operation.  The  sifting  is  performed  as  before,  and  the  remains  go  to  the 
fourth  mill,  &c. 

The  tails  of  sifter  No.  4  pass  to  the  rolls  A,  whence  the  product 
runs  to  the  centrifugal,  which  produces  dark  flour  and  dark  dunst  as 
throughs  and  tails  over  the  branny  particles,  which  are  sent  to 
the  last  break  to  be  cleaned  up.  The  dark  dunst  goes  to  the  last  (6) 
reduction  roll. 

The  dunst  of  the  second  middlings  goes  to  the  third  reduction  mill  (3) 
and,  together  with  the  remains  of  the  first  dunst,  is  reduced. 

The  flour  after  sifting  is  collected  in  bags  or  in  a  bin.  The  remaining 
dunst  passes  to  the  fourth  reduction  (4),  and  is  ground  together  with  the 
dunst  of  the  third  middlings. 

The  tails  (dark  dunst)  of  the  first  and  the  last  sieves  of  the  sifters 
Nos.  I  to  V  are  sent  to  the  reduction  roll  (6).  The  break  dunst  III  is 
also  admixed  to  it. 

The  break  dunst s  (I,  II,  and  III),  blended  with  the  middlings  dunst, 
are  in  comparison  to  it  less  valuable,  since  they  are  formed  of  particles 
lying  closer  to  the  integument,  whereas  the  middlings  dunst  lies  nearer 
the  central  parts  of  the  grain.  Therefore  the  break  dunsts,  even  should 
they  be  perfectly  white  in  appearance  after  purification,  can  be  blended 
with  middlings  dunst  only  when  the  latter,  arrived  at  the  mill  (4).  has 


CHAP,  vm]  FLOUR   MILLING  511 

already  lost  somewhat  in  its  quality  owing  to  the  reduction  of  the 
mealy  particles  on  the  three  preceding  rolls. 

To  the  fifth  reduction  mill  there  go  the  dunst  from  the  mill  (4),  the 
middlings  dunst  (from  sifter  No.  IV)  and  the  second  quality  break  dunst. 
From  the  sifter  of  that  mill  (sifter  No.  V)  the  flour  is  sacked  off,  and  the 
throughs  of  all  sieves,  together  with  what  remains  of  the  tails  from  the 
four  preceding  sifters,  with  the  third  cleaned  break  dunst  and  the  dunst 
from  the  centrifugal,  are  sent  to  the  sixth  reduction  mill.  The 
flour  is  sacked,  while  all  the  tails  is  directed  to  the  seventh  mill  B. 
The  latter  likewise  receives  the  inferior  dunst  from  the  rest  of  the 
breaks.  For  bolting  there  is  the  centrifugal  b.  Here  everything  is 
collected  in  sacks  or  bins  and  the  reduction  of  the  middlings  and  dunst 
is  ended. 

One  more  mill  or  stone  C  should  be  put  in  to  treat  the  products 
which  suit  nowhere,  as  well  as  for  cleaning  the  bran.  For  bolting  the 
product  of  this  mill  there  is  again  a  centrifugal  or  sifter,  all  the  products 
of  which  are  sacked  off  separately. 

Under  the  reduction  mills  should  be  stationed  detachers,  shown  in 
the  diagram,  otherwise  the  produce,  sometimes  crushed  into  flat  flour 
flakes,  cannot  be  properly  bolted. 

For  rolls  followed  by  centrifugals  there  is  no  special  need  to  have 
detachers,  as  the  distributing  beaters  of  the  centrifugals  break  up  the 
thin  film-like  flakes  of  mealy  product,  formed  through  the  strong  pressure 
of  the  roller  surfaces  upon  it. 


SHORTER  GRADUAL  REDUCTION  SYSTEMS 

3Jhe  abbreviated  or  semi-high  (Halbhochmullerei)  grinding  is  charac- 
terised mainly  by  a  reduced  number  of  breaks  and  rebreaks  (the  latter 
may  be  totally  absent),  by  a  curtailed  grading  according  to  size  (the 
absence  of  middlings  grading  sifters)  and  quality,  a  reduction  in  the 
number  of  rebreaks  for  middlings,  and  finally  a  lessened  number  of 
reductions. 

The  resultant  influence  of  abridgment  in  the  high  grinding  scheme 
becomes  noticeable  first  of  all  in  the  fact  that  the  yield  of  the  best  grades 
of  flour  diminishes,  and  the  quality  of  all  the  grades,  except  the  first  and 
partly  the  second,  becomes  inferior ;  this  is  especially  brought  about  by 
the  reduction  in  the  number  of  purifiers,  i.e.  the  abbreviation  of  the  process 
of  grading  the  product  according  to  quality. 


512 


FLOUR    MILLING 


[CHAP,  vin 


Let  us  examine  a  few  shorter  gradual  reduction  diagrams. 

German  Abridged  High  Grinding. — The  mill  grinds  2000  bushels  of 
wheat  per  day  (24  hours).  In  the  diagram  (Fig.  504)  there  are  seven 
breaks,  the  first  one  (Hochschrot)  being  designed  to  split  the  grain  in 


FIG.  504. 

two  down  the  crease.  After  the  passage  through  the  high  break  the 
product  goes  to  a  brush  duster,  which  gives  break  middlings  as  tails, 
and  blue  flour  (a  dirty  greyish-blue  flour  with  dust)  as  throughs.  The 
further  process  of  breaking  is  performed  in  the  usual  order  with  grading 
of  the  break  chop  on  sifters.  The  characteristic  feature  here  is  the  high 
numbers  of  wire  sieves  starting  with  No.  24.  and  the  correspondingly 


CHAP,  vm]  FLOUR   MILLING  513 

higher  numbers  of  all  the  sieves  in  the  sifters.  That  suggests  the  grind- 
ing surfaces  of  the  corrugated  rolls  have  been  brought  close  up  together  ; 
through  these,  in  fact,  the  finer  and  more  flaky  flour  is  prepared. 

In  watching  the  breaking  process  in  the  diagram,  we  see  the  follow- 
ing picture. 

The  unfinished  break  stock  passes  as  usual  to  the  next  break,  and 
finally  the  tails  of  No.  36  sifter  of  the  seventh  break  are  large  bran,  which 
goes  to  be  cleaned  on  the  bran  duster  (brush) .  From  the  thirty-sixth  to  the 
thirty-eighth  number  of  the  second,  third,  and  fourth  breaks  large  semo- 
lina is  obtained,  which  in  our  milling  systems  would  constitute  rebreak 
semolina. 

This  semolina,  as  well  as  the  fine  middlings  from  the  same  sifters,  goes 
to  the  grading  for  middlings  (one  may  say  the  controlling)  sifter,  which 
sorts  separately  the  large  and  the  fine  semolina.  The  tails,  large 
semolina,  which  ought  to  be  directed  to  a  separate  rebreaking  roll,  is 
sent  to  the  fourth  break,  which  acts  the  part  of  a  rebreak. 

That  is,  properly  speaking,  the  first  item  of  abridgment  of  the  milling 
process. 

The  fine  and  the  large  middlings  graded — each  into  two  kinds — are 
subjected  to  further  sorting  on  a  purifier  of  the  "  Nemelka  "  type.  The 
tails  of  the  chop  from  breaks  5  and  6  mix  with  the  tails  from  the  middlings 
sieves  of  the  same  systems  in  the  later  breaks,  while  their  fine 
middlings  are  cleaned  on  purifiers  of  the  "  Reform  "  type.  The  dunsts 
of  the  second,  third,  and  fourth  breaks  are  mixed  together  and  cleaned  on 
a  purifier  of  the  same  type.  The  dunst  from  the  fifth  break  is  purified 
separately,  while  the  fine  dunst  of  the  sixth  and  seventh  breaks  go  to  be 
reduced  :  the  first  on  the  last  reduction  roll,  and  the  second,  together 
with  the  fine  semolina,  on  the  stone  mill.  The  fine  middlings  from  the 
fifth  and  sixth  breaks  are  graded  apart,  on  purifiers  C  and  D.  having 
besides  that  a  controlling  purifier  B. 

The  process  further  consists  in  that  the  graded  middlings  go  to  be 
rebroken  in  the  second  row  of  roller  mills  with  smooth  rolls.  A  charac- 
teristic point  in  that  part  of  the  process  is  the  deflection  of  the  middlings 
refuse  to  the  fifth,  sixth,  and  seventh  break  systems,  which  we  must 
acknowledge  to  be  expedient. 

The  dunsts  from  these  systems  go  to  be  finally  reduced.  So  the  grad- 
ing of  dunst  according  to  quality  is  absent  here,  and  this  causes  the  tails 
from  the  sifters  of  the  middlings  rebreak  to  be  directed  to  the  fifth  and 
seventh  reductions.  The  absence  of  these  purifiers  is  the  second  material 

abridgment  in  the  process, 
• 


514  FLOUR   MILLING  [CHAP,  vm 

We  shall  not  speak  of  the  further  details  in  the  diagram,  the  rest 
being  sufficiently  clear.  The  grading  of  flour  is  not  given  in  the  diagram, 
as  it  depends  to  a  considerable  degree  on  the  brands  sold  by  any  par- 
ticular mill. 

The  general  data  characterising  the  dimensions  of  the  roller  mills  are 
as  follows  :  the  break  systems  have  rolls  1000  x250  mm.  ;  the  reduction 
systems  1000  x  300  mm.,  and  finally,  the  stone  mill  1300  mm.  in  diameter. 
All  the  stock  is  bolted  on  sifters,  except  that  the  stone  mill  is  followed 
by  a  centrifugal. 

American  or  English  Grinding. — The  diagram  introduced  to  our 
attention  (Fig.  505)  is  a  characteristic  scheme  of  American  or  English 
high  grinding,  which  must  be  classed  with  the  abridged  high  grinding  of 
the  European  type  as  it  is  accepted  with  us.  In  this  scheme  the  system 
of  rebreaks  is  absent  and  the  number  of  breaks  is  reduced  to  five,  and  the 
reduction  process  is  very  much  curtailed,  containing  at  the  same  time  no 
purifiers  for  the  rebreak  of  middlings.  By  reason  of  the  latter  circum- 
stance one  is  obliged  to  use  the  purifiers  which  sort  the  break  product. 
The  diagram  (Fig.  505)  is  for  a  mill  in  the  State  of  Kansas  working  on 
hard  wheat  and  having  a  capacity  of  280  sacks  per  twenty-four  hours. 

It  may  be  seen  in  the  diagram  that  there  are  five  breaks  and  nine 
reductions  here.  The  five  breaks  are  characterised  by  the  dimen- 
sions of  the  rolls  successively — 9  in.  x30  in.,  9  in.  x30  in.,  9  in.  x30  in., 
9  in.  x  24  in.,  and  9  in.  x  24  in.,  and  by  the  differentials  of  the  rolls  of  the 
fast  to  the  slow,  in  the  same  succession  from  the  first  break  to  the  fifth — - 
3  :  1,  3  :  1,  3  :  1,  2f  :  1,  and  2|  :  1. 

The  aim  of  this  mill  was  to  yield  as  much  flour  of  the  first  grade 
(patents)  as  possible,  and  therefore  on  turning  to  the  diagram  we  see  that 
the  flour  from  all  the  break  sifters,  except  the  fifth,  and  from  all  the 
reduction  sifters,  except  the  last  three,  is  sent  to  patents.  Still,  how- 
ever, there  is  a  combination  for  sending  the  flour  from  the  break  sifters  to 
the  second  grade  (clear). 

It  is  interesting  to  note  the  grading  of  middlings.  The  purifier 
No.  1  receives  the  coarse  semolina  from  No.  34  sieves  of  the  first  three 
break  sifters.  This  purifier,  as  well  as  all  the  others  (see  the  arrange- 
ment of  the  sieves,  the  order  of  their  Nos.),  is  arranged  to  give  light  offals 
which  run  to  the  filter  DC,  heavy  offals  which  go  from  No.  1  to  the  fine 
bran  (feed),  and,  finally,  the  throughs.  The  throughs  from  the  purifier 
No.  1  mixed  with  the  throughs  from  sieve  No.  26  of  the  second  purifier 
(No.  2)  go  to  the  smooth  rolls  9  in.  x24  in.  The  Americans  call  that 
the  first  rebreak  or  "  sizing  "  of  middlings. 


CHAP.    VIII] 


FLOUR    MILLING 


515 


Fio.  505, 


516  FLOUR    MILLING  [CHAP,  vin 

It  must  be  noted  that  the  Americans  have  no  rebreak  grooved  rolls 
in  their  break  system  at  all,  and  in  that  respect  their  milling  -process  is 
greatly  curtailed  in  comparison  with  the  German  and  Hungarian. 

Proceeding  further ,  we  see  that  the  same  three  break  sifters  pass  fine 
semolina  tails  off  the  sieves  No.  64  to  the  purifier  No.  2.  The  throughs 
from  the  sieve  No.  26  go  to  the  first  sizing  roll,  as  we  have  seen, 
while  the  Nos.  from  58  to  34  send  the  cleaned  middlings  to  the  first 
reduction. 

The  heavy  offals  from  this  purifier,  like  those  from  No.  3,  go  to  the 
smooth  rolls  for  a  second  middlings  sizing  (rolls  9  in.  x24  in.,  and  differ- 
ential 1J  ;  1),  mixing  with  the  tails  of  the  first  middlings  roll.  From 
the  point  of  view  of  the  Russian  millers,  such  blending  is  a  downright 
crime.  But  we  must  not  forget  that  the  Americans  produce  only  three 
or  four  grades  of  flour,  and  in  the  given  case  there  is  the  wish  to  obtain 
the  greatest  quantity  of  patent  flour. 

The  purifiers  Nos.  5  and  6  purify  the  finer  middlings  :  No.  5  from  the 
B.M.R.  sifter,  which  grades  the  throughs  of  sieves  Nos.  64-68  of  the  first 
four  break  sifters,  and  No.  6  of  the  fifth  break  sifter  and  of  the  last 
reduction  sifter. 

Besides  the  sifter  we  have  yet  two  centrifugals  (13xx-64,  14xx-llxx) 
and  two  brush  dusters  SD  and  ED.  The  throughs  of  the  centrifugals 
run  to  the  second  and  third  grade  of  flour,  while  the  tails  (as  well  as 
the  tails  from  the  brush  8D)  goes  to  the  fine  bran.  The  throughs  of  the 
brushes  pass  to  the  redressing  sifter  R  and  the  tails  from  the  brush  ED 
yields  large  bran.  DC  designates  the  fans. 

We  need  not  dwell  on  the  operation  of  the  reduction  rolls,  as  the 
mining  process  is  easily  traced  in  the  diagram. 

Hungarian  Milling  Process.— Fig.  506  illustrates  the  diagram  of  an 
automatically  working  mill,  after  the  system  of  which  many  mills  have 
been  erected  in  Hungary  in  recent  years.  The  wheat  brought  by 
customers  is  milled  not  in  separate  lots,  but  mixed  together  according 
to  quality.  Having  first  ascertained  the  weight  of  wheat,  it  is  de- 
spatched to  the  cleaning  department.  After  milling  the  customer 
receives  the  quantity  of  flour  corresponding  to  the  weight  of  the  wheat 
brought  by  him. 

Since  the  wheat  is  not  milled  separately,  it  is  natural  that  the  cus- 
tomer does  not  receive  the  actual  gotten  out  of  his  own  wheat ;  but 
in  order  to  serve  everybody  equally  well,  even  if  the  goods  supplied  are 
different  in  quality,  the  good  wheat  of  equal  quality  belonging  to  several 
customers  is  mixed  and  milled,  and  then  a  worse  wheat,  but  also  equal 


CHAP.    VIII] 


FLOUR   MILLING 


517 


518  tfLOUR   MILLING  [CHAP,  viii 

in  quality,  is  ground.  Such  a  method  affords  the  possibility  of  satisfy- 
ing everybody. 

That  arrangement  contains  no  rebreak  rolls,  as  the  coarse  rebreak 
middlings  go  to  the  break  rolls.  The  reduction  of  middlings  and  dunst 
is  performed  with  the  aid  of  six  pairs  of  smooth  rolls  of  hardened  cast 
iron,  which  are  marked  in  the  diagram  by  figures  1-6. 

The  cleaning  up  of  the  low  grade  stock  and  fine  bran  is  done  on  a  pair 
of  finely  fluted  rolls  of  hardened  cast-iron  and  on  a  millstone. 

After  the  reduction  the  middlings  and  dunst  before  bolting  pass 
through  the  detacher  D.  The  seventh  break  and  bran  to  be  cleaned 
previously  to  going  to  the  sifter  run  through  the  centrifugal  C,  to  free  the 
coarse  tails  of  dunst  and  flour  and  shake  up  once  more  the  remains  to 
be  sifted. 

The  bolting  system  consists  of  Haggenmacher  s  sifter  with  six  sections, 
containing  6x11  trays.  The  first  high  break  is  treated  on  the  smaller 
part  of  this  bolting  apparatus. 

For  bolting  the  reduced  middlings  and  dunst  there  is  also  a  sifter  with 
six  sections  and  6x9  trays  and  a  small  sifter  of  the  same  construction 
with  2x9  trays.  The  purification  is  divided  into  three  systems,  and 
consists  of  two  purifiers  of  the  Haggenmacher  type  with  eight  sections 
and  one  with  four  sections  O.  In  the  machine  with  eight  sections  are 
purified  the  middlings  from  the  second  and  fifth  breaks;  the  smaller 
machine  receives  the  fine  middlings  from  the  sixth  break. 

There  are  two  purifiers  with  ten  sections.  To  the  first  half  there  goes 
the  dunst  from  the  third  and  fourth  breaks  to  the  second — that  of  the 
second  and  third  breaks.  The  second  machine  purifies  the  tails  of  the 
first  machine,  the  dunst  from  the  purifiers,  and  the  break  dunst  from  the 
sixth  break.  The  first  break  is  kept  very  high,  and  bolted  on  a  steel 
sifting  cloth  Nos.  18  and  26.  The  tails  of  No.  26  are  coarse  middlings 
which  pass  to  the  sixth  break,  while  the  throughs  go  to  the  last  break. 
In  the  following  breaks  the  grain  is  gradually  reduced  so  that  the 
seventh  break  yields  clean  broad  bran.  The  upper  three  trays  of  the 
break  sifter  are  furnished  with  a  coarse  bolting  cloth  which  separates 
away  the  tails,  the  coarse  and  the  fine  middlings.  The  throughs 
pass  on  to  the  next  flour  sieves,  which  yield  as  tails  dunst  to  be 
cleaned. 

The  middlings  directed  to  the  purifiers  G,  by  means  of  a  small  sifter 
stationed  at  the  top  of  the  machine,  are  sorted  in  eight  grades  according 
to  size,  and  each  grade  passes  into  one  of  the  eight  divisions  of  the  machine, 
where  every  one,  of  them  is  purified  separately.  The  coarse  tailings  of 


CHAP.  vin]  FLOUR    MILLING  519 

the  feeding  sieve  of  the  grading  sifter  return  to  the  break  rolls,  while  the 
fine  throughs  from  the  last  sieve  go  to  the  dunst. 

The  pure  middlings  from  the  first  and  second  purifiers  are  directed  to 
the  rolls  2.  The  heavier  liftings  of  the  first  machine  are  cleaned,  together 
with  the  middlings  of  the  second  and  fifth  breaks.  The  heavier  liftings  of 
the  second  purifier  go  with  the  middlings  of  the  fourth  break,  to  the  small 
fourth  purifier.  The  pure  middlings  from  that  machine  pass  to  the  fifth 
reduction  rolls,  the  liftings  to  the  sixth  system.  All  the  branny  stock 
from  the  three  purifiers  goes  to  the  seventh  break. 

The  purifiers  Z  are  divided  into  two  equal  groups.  The  first  group 
receives  dunst  from  the  third  and  fourth  breaks,  the  other  that  of  the 
second  and  fifth  breaks.  Both  the  tails  of  that  machine  are  added 
to  the  middlings  of  the  second  and  fifth  breaks.  The  pure  dunst  of  the 
first  half  of  the  machine  and  the  first  fine  pure  dunst  of  the  second  half 
are  the  product  of  the  third  reduction  roll.  The  tails  of  the  first  machine 
are  cleaned  by  the  second.  The  pure  dunst  from  that  machine  yields  a 
product  for  the  fifth  reduction  roll.  The  tails  go  to  the  last  break  rolls. 

The  product  running  from  the  reduction  rolls  to  the  sifter  is  divided 
into  a  coarse  and  a  fine  tails  and  several  grades  of  flour.  For  that  pur- 
pose in  every  sixth  part  of  the  sifter  there  is  a  scalping  sieve  and  several 
flour  sieves.  The  tails  of  the  scalping  sieve  in  the  first  four  reduction 
roller  systems  go  to  the  sixth  break.  The  tails  of  the  fifth  and  sixth 
systems  are  directed  to  the  seventh  break.  The  dunst,  according  to 
its  quality,  is  despatched  to  the  reduction  system. 

With  this  semi-high  milling  process  there  are  obtained  only  four 
grades  of  flour,  which  from  the  sifters  go  to  collecting  worms  and,  totally 
blended  in  them,  are  delivered  into  sacks. 

French  Milling  System. — In  Fig.  507  is  given  a  typical  scheme  of 
high  French  grinding,  which,  from  our  standpoint,  should  likewise  be 
referred  to  the  abridged  high  grinding. 

A.  Coarse  semolina  from  the   first  four  break  mills  go  to  the  first 
purifier  to  be  treated  and  thence  to  the  first  reduction  to  be  reduced. 

B.  Fine  semolina  from  the  first  four  break  mills  go  to  the  second 
purifier,  and  thence  to  the  second  pair  of  rolls  of  the  first  reduction  mill. 

C.  Middlings  from  the  second,  third,  and  fourth  break  mills  go  to  the 
fourth  reduction  mill. 

Cj.  Middlings  from  the  second  reduction  mill  go  to  the  fourth  reduc- 
tion mill. 

D.  Tails  (dunst)  from  the  fifth  break  mill  and  from  the  second  puri- 
fier pass  to  the  third  purifier  and  thence  to  the  third  rebreak  mill. 


520 


FLOUR   MILLING 


[CHAP,  vni 


E.  Middlings  from  the  first  reduction  mill  go  to  the  second  reduction 

mill. 

F.  Middlings  from  the  sixth  break^milljpass  to;thelfourthfpurifier  and 
thence  to  the  fifth  reduction  mill. 

F!.  Tails  from  the  first  and  third  reduction  mills  go  to  the  fifth. 


Oascuieaatomalique 


Son*  U>      5oa»  gro 


Centrifuge  metallique— Centrifugal  with  metal  Refus— Tails  or  to  offals. 


cloth. 
Sasseur — Purifier. 

Bluterie  ronde  de  surete— Round  redresser. 
Bluterie  ronde  divisenr — Grading  reel. 
Detacheur— Detacher. 


Bascule  automatique— Automatic  scale. 
Ble  propre — Pure  grain. 
Appareil  magnetique— Magnetic  apparatus. 
Extracteuse  ronde— Round  reel. 
Centrifuge— Centrifugal . 

FIG.  507. 


G.  Tails  from,  the  fourth  reduction  mill  (after  the  centrifugal)  and 
the  product  No.  40  from  the  fifth  go  to  the  sixth. 

H.  Tails  from  the  third  and  sixth  reduction  mills  and  the  product- 
No.  28  from  the  fifth,  go  for  final  treatment  to  the  seventh  reduction  mill. 


CHAP,  vm]  tfLOUR   MILLING 

Hj.  Tails  from  the  fourth  purifier  go  to  the  seventh  reduction  mill  or 
the  offal  sorter,  depending  on  the  quality  of  the  product. 

I.  Fine  sharps  (thirds,  etc.). 

J.  Coarse  sharps  (Pollard,  etc.). 

K.  Coarse  Pollard. 

Kj.  Fine  bran. 

L.  Tails  from  the  first  and  third  purifiers  go  to  the  sixth  break 
mill. 

Lj.  Liftings  from  the  first,  second,  and  third  purifiers  go  to  the  centri- 
fugal with  wire  cover  for  the  extraction  of  flour  out  of  them. 

M.  Dark  flour. 

Mx.  Dunst  from  the  first  break  mill.  If  the  products  seem  to  be  good 
they  may  be  reduced  on  the  sixth  break  mill. 

N.  Flour  from  the  second,  third,  fourth,  and  fifth  break  mills. 

Nj.  Flour  from  the  first,  second,  third,  fourth,  fifth,  and  sixth  reduc- 
tion mills. 

0.  Dark  flour  from  the  sixth  break  mill. 

Oj.  Dark  flour  from  the  seventh  reduction  mill. 

P.  Fine  bran  from  the  wire-covered  centrifugal. 

Q.  Broad  bran. 

The  flour  from  the  fifth  break  mill  and  sixth  reduction  mill  is  sent 
further  in  the  manner  answering  the  wish  to  obtain  a  greater  or  smaller 
quantity  of  flour  of  the  highest  grade. 

If  the  tails  of  the  fourth  purifier  is  not  of  much  value  for  baking,  it 
may  be  directed  to  the  seventh  reduction  mill  with  a  centrifugal,  having 
previously  subjected  it  to  strong  aspiration. 

Very  Short  Milling  Systems. — The  desire  to  make  the  equipment 
of  a  mill  cheaper,  and  at  the  same  time  to  obtain  as  good  a  flour  as  pos- 
sible, compels  one  to  have  recourse  to  the  extremely  abridged  milling 
process,  an  example  of  which  may  be  taken  in  the  form  of  a  diagram  of 
an  American  process  for  mills  of  from  100  to  200  sacks  capacity. 

According  to  the  diagram  (Fig.  508)  we  have  but  four  break  systems 
with  corresponding  differentials  :  for  the  first  system  2:1,  second  2:1, 
third  2J  :  1,  and  for  the  fourth  3:1.  The  number  of  corrugations  for 
the  first  system  is  12  to  1  in.,  for  the  second  16,  for  the  third  20,  and  for 
the  fourth  24.  It  must  be  noted  at  the  same  time  that  often  these 
limits  are  changed  from  18  (instead  of  12)  to  28  (instead  of  24)  corruga- 
tions to  an  inch.  The  length  of  rolls  is  30  in.  and  their  diameter  9  in. 

The  whole  process  of  milling  takes  course  as  follows  :  from  the  first 
break  system  the  product  runs  to  the  sifter  on  to  the  distributor  (or,  what 


£22 


MILLING 


[CHAP,  vm 


the  Germans  call  Sammelboden),  whence  it  passes  to  the  wire  sieve  No.  18 
(18-w).  The  tails  of  the  scalping  sieve  No.  18  go  to  the  second  break, 
the  middlings  from  No.  44  to  the  purifier  Kx.  It  is  supposed  that  all  the 
large  middlings  are  separated  away,  and  from  the  Nos.  10,  11  and  12'  of 
flour  sieves  the  throughs  yield  flour,  which  goes  to  the  second  grade 
(bakers'),  while  the  refuse  off  No.  12  passes  to  the  purifier  K 2  for  medium 
middlings. 

Further,  if  we  watch  the  second,  third  and  fourth  breaks,  we  shall 
see  that  the  preceding  process  of  grading  the  middlings  and  flour  is  per- 
fectly and  accurately  repeated  :  all  the  tails  off  the  middlings  sieves 
go  to  the  purifier  Kl3  the  throughs  from  the  flour  sieves  to  the  second 


FIG.  508. 

grade  of  flour,  and  the  tails  of  the  last  sieves  (llxx,  llxx,  and  12xx) 
to  the  purifier  K 2.  As  to  the  tails  from  the  scalping  sieve  No.  34  of  the 
last  break  sifter,  it  runs  to  the  bran  duster  ED. 

Laying  aside  for  the  present  the  possible  variations  which  are  shown 
in  the  diagram,  let  us  direct  our  attention  to  the  work  of  the  reduction 
rolls.  Roll  5  (9  in.  x24  in.)  receives  the  throughs  (pure  middlings)  of 
the  purifier  K{,  rolls  6-7  (9  in.  x24  in.)  the  cut-off  and  tails  from  the 
purifiers  Kl  and  K2,  rolls  8-9  (9  in.  x  18  in.)  the  throughs  from  K2,  roll 
No.  10  (9  in.  x24  in.)  the  throughs  from  the  purifier  Ks,  and,  finally, 
roll  12  (9  in.  x25  in.)  receives  the  cut-off  and  tails  from  the  purifier  Ks. 

First  of  aU,  we  must  note  that  the  flour  from  all  the  sifters  corre- 
sponding to  the  six  reductions  goes  to  one  first  grade,  generally  named 
Patent. 

The  tails  from  the  sifters  E  and  G  (first  and  third)  go  to  the  purifier  K9, 


CHAP,  vmj  FLOUR   MILLING 

the  tails  of  sifter  F  to  the  purifier  K2)  while  the  tails  of  the  sifters  / 
and  H  pass  to  the  eleventh  (9  in.  X24  in.)  finishing  roll,  after  which 
the  throughs  of  the  centrifugal  (No.  14xx)  go  to  the  second  grade, 
and  the  tails  go  to  the  second  centrifugal,  which  gives  the  last  worst 
grade  (low  grade)  as  throughs,  sending  the  tails  to  the  brush  duster 
SD.  From  the  machine  last  mentioned  fine  bran  is  obtained  as  tails,  and 
the  throughs  are  deflected  to  the  second  centrifugal. 

In  the  diagram  Q  denotes  the  fan,  and  P  the  dust-collectors,  which 
despatch  the  products  also  to  the  second  centrifugal. 

In  this  manner  we  have  followed  the  main  details  of  the  preparation 
of  flour  of  the  first,  second,  and  third  grade.  It  must  be  pointed  out 
that  the  tails  No.  44  of  the  sifter  F  likewise  goes  to  the  bran  duster  BD, 
which  tails  over  large  bran. 

In  recapitulating  the  general  run  of  the  diagram  we  may  say  that  the 
first  grade  (Patent)  is  obtained  by  the  Americans  by  reducing  the  purified 
middlings,  i.e.  from  all  the  reduction  systems  in  the  throughs  of  the  flour 
sieves  of  the  sifter ;  the  second  grade  (Bakers')  from  the  flour  sieves  of  the 
break  systems,  the  third  grade  (low  grade)  from  the  cleaning  up  rolls. 

The  first  variation  V \  affords  the  possibility  of  sending  the  throughs 
of  the  last  break  sifter  D  (sieve  12)  to  the  last  reduction  sifter  H,  to  be 
controlled  as  it  were ;  by  the  variation  F2  the  middlings  from  the  last 
break  sifter  D  are  directed  to  the  purifier  K 2  or  K3,  which  is  more  reason- 
able than  to  KI  which  purifies  the  heavy  and  large  middlings.  By 
the  variation  F3  the  throughs  of  the  bran  duster  are  directed  to  be  redressed 
in  the  sifter  H ;  by  the  variation  F4  the  large  and  the  fine  bran  SS 
may  be  mixed  ;  by  variation  F5  the  first  grade  is  improved  by  excluding 
the  flour  from  the  fourth  and  fifth  reductions  ;  finally,  in  variation  F6  the 
first  and  second  grades  are  blended  together  and  produce  the  medium 
sort  (Straight),  in  other  terms,  the  whole  grist  is  divided  into  two  grades 
of  flour  (straight  and  low  grade). 

In  Fig.  509  we  have  a  diagram  of  an  extremely  short  system 
suggested  by  Baumgartner.  The  grain  runs  to  the  Hochschrot  with 
one  corrugated  and  one  smooth  roll.  After  it  has  been  broken  down 
the  crease  here  the  grain  passes  to  the  brush  scalper,  which  yields  as 
throughs  blue  flour  or  offals,  which  depends  on  how  drastically  and  rigor- 
ously the  grain  is  treated  on  the  Hochschrot.  Further,  the  product  is 
subjected  to  a  triple  break,  and  is  cleaned  up  on  the  fifth  corrugated 
passage,  which  produces  branny  flour  e,  feed  /,  and  large  bran  g. 

After  the  first  break  mill  the  product  is  bolted  on  a  plansifter.  The 
flour  is  then  sacked  off  as  second  grade. 


524 


FLOUR   MILLING 


.    VITl 


The  tails  go  to  the  second  break.  The  semolina  passes  into  a  purifier 
with  an  inside  sieve  of  four  sections,  the  fine  middlings  to  a  purifier  for 
dunsts  of  a  similar  construction. 

From  the  second  break  there  is  obtained  bolted  flour  of  the  second 
grade,  coarse  and  fine  middlings,  which  go  to  the  corresponding  purifiers. 
The  tails  run  to  the  third  break  mill.  The  flour  produced  here  is  turned 
to  the  third  grade,  a  small  quantity  of  middlings  and  dunst  are  directed 
to  the  purifier,  the  integuments  and  coarse  tailings  go  to  the  last  break 
mill.  The  reduction  stock  from  this  roll  is  graded  on  a  hexagon  reel, 
and  yields  the  products  e,  /,  and  g  spoken  of  above. 


^ 

\               \ 

^ 

-^ 

^_^ 

i  j      1  • 

_-.:--. 

1      r- 

^7 

1     rj 
1     f- 
—  J      r  ~ 

I',      -- 

•   

hj.^ 

4  4 

[_ 

'   I 

-t-  -!- 

-J 

.^        I 


FIG.  509. 

The  liftings  of  the  purifier  are  sacked  off,  as  ready  product-bran.  The 
tails  from  the  middlings  sieves  are  directed  to  the  second  break,  the  tails 
of  the  fine  stock  go  with  the  middlings  from  the  purifier. 

The  pure  middlings  pass  to  the  first  smooth  rolls,  thence  to  the  detacher 
and  plansifter.  Here  second  grade  flour  i  is  obtained. 

The  coarse  stock  is  turned  to  the  third  smooth  roll,  while  the  fine 
middlings  go  to  the  second.  The  latter,  after  it  has  been  ground  and 
loosened,  is  bolted  on  a  plansifter,  and  produces  flour  of  the  first  grade  k. 
Only  the  less  coarse  parts  pass  to  the  third  smooth  mill,  to  which  likewise 
the  worst  middlings  from  the  purifier  are  turned. 

After  reduction  and  sifting  a  flour  of  the  second  grade  I  is  produced 
here.  The  larger  tails  go  to  the  second  dunst  millstone,  the  finer  parts 
go  to  be  recleaned  in  the  middlings  purifier.  Now  they  are  made  equivalent 


CHAP.    VIII] 


FLOUR   MILLING 


525 


I  •«» 

*g*-4~ 


526  FLOUR   MILLING  [CHAP,  vm 

to  the  break  middlings.  The  purified  break  midds  pass  to  the  first  midds 
millstone  and  yield  after  bolting  flour  of  the  second  grade  m.  The  tails 
go  to  the  second  millstone,  and  after  reduction  to  the  centrifugal,  which 
yields  flour  of  the  third  grade  n,  and  fine  bran  as  overtails. 

The  corrugated  rolls  should  be  300  mm.  in  diameter  and  have  1  :  2J 
differential,  the  smooth  rolls  350  mm.  in  diameter  and  the  2  :  3  differ- 
ential. 

We  must  add  that  this  abridged  diagram  cannot  produce  the  fine 
grades  of  flour  obtainable  in  high  and  semi -high  grinding. 

Still  the  grades  of  flour  received  are  pure  and  fetch  fair  prices ; 
at  the  same  time  it  must  be  borne  in  mind  that  to  obtain  them  less 
machinery  is  needed,  and  therefore  the  expenditure  of  original  capital 
is  less. 

Semi-automatic  Grinding. — Up  to  the  present  we  have  been  examin- 
ing plans  of  automatic  mills,  in  which  from  the  feeding  in  of  the  grain  to 
the  delivery  of  the  flour  the  whole  process  is  performed  without  the 
assistance  of  mill  hands.  Since  semi-automatic  mills  are  still  used  in 
Russia  we  append  the  general  type  of  a  scheme  (Fig.  510)  of  such  a  mill, 
which  is  characterised  by  the  limited  number  of  reduction  machines. 

The  wheat  is  poured  into  the  hopper  and  carried  by  the  elevator  to 
the  automatic  scale  a,  and  thence  to  the  separator  &,  which  is  furnished 
with  a  large  meshed  sieve.  That  sieve  removes  the  larger  impurities- 
stones,  wood,  &c.  The  sand  and  dust  are  separated  away  with  the  aid 
of  a  second  sieve  and  travel  to  the  outlet.  The  cleaned  grain  passes 
through  the  sieve  to  the  dust  cleaner  or  separator,  whence  the  lighter 
particles  are  driven  by  the  fan  into  the  dust -collecting  tubular 
pressure  filter.  The  wheat  cleaned  in  this  manner  passes  to  two 
cockle  cylinders  c.  The  re-cockls  cylinder  cx  separates  the  half 
grains  from  the  cockle.  Through  the  magnet  apparatus  the  product 
runs  to  the  elevator,  which  lifts  it  to  the  horizontal  scourer.  In  that 
machine  iron  beaters  throw  the  grain  against  a  sieve  of  steel  wire,  to  separ- 
ate away  the  yet  remaining  dust  and  beard.  The  separate  particles  are 
carried  to  the  pressure  tubular  filter  d  by  a  strong  air  current.  The 
filter  is  divided,  and  one  part  serves  for  the  separator,  the  other  for  the 
scourer. 

The  total  number  of  tubes  of  the  filter  is  2  x  60  =  120.  After  the  ver- 
tical scourer  the  wheat  flows  into  a  horizontal  emery  one,  on  which 
the  grain  coverings  are  partly  torn  off.  The  light  particles  separated 
away  are  blown  into  the  first  half  of  the  pressure  tubular  filter  d,  and 
the  grain  by  means  of  the  elevator  passes  into  the  vertical  brush  machine 


CHAP,  vm]  FLOUR    MILLING  527 

h,  where  it  is  freed  of  the  dust  lying  in  the  crease  of  the  grain  and  falling 
in  during  the  cleaning.  The  separate  particles  go  to  the  second  half  of 
the  pressure  tubular  filter  d,  likewise  with  120  tubes.  The  perfectly  cleaned 
wheat  flows  now  into  the  bin,  and  thence  to  three  pairs  of  corrugated  rolls 
(650x220,  i,  iv  I),  on  which  it  is  subjected  to  break  six  times.  The 
cleaned  wheat  runs  from  the  bin  mentioned  to  the  first  half  of  the  roller 
mill  i.  The  first  break  chop  by  means  of  the  elevator  is  lifted  to  the  first 
quarter  of  the  sifter  k.  The  tails,  separated  on  sieve  No.  20,  goes  to 
the  second  half  of  the  hopper  ;  the  sieve  No.  36  separates  coarse 
semolina,  sieve  No.  15  first  grade  of  flour,  the  tails  of  No.  12  yields 
midds  to  be  purified,  sieve  No.  8  dunst  to  be  reduced.  In  this  manner  the 
further  breaking  is  performed,  and  the  wheat  is  subjected  to  break  six  times. 
The  mill  ^  serves  for  reducing  the  coarse  semolina  and  midds,  and  has 
two  pairs  of  smooth  rolls,  650  x  220  in  size.  The  semolina  and  middlings 
are  subjected  to  cleaning  on  purifier  o.  That  machine  is  connected  with 
one  pressure  tubular  filter  d>2,  with  120  tubes.  The  purified  middlings  go 
to  the  second  pair  of  rolls  m  and  to  the  second  quarter  of  the  sifter  6lt 
Since  the  middlings  in  passing  through  the  rolls  are  crushed  into  thin 
flour  flakes,  before  the  sifter  there  are  placed  detachers  ppl}  which  loosen 
these  flakes  and  thus  quicken  the  grading.  The  purified  midds  go  to 
the  first  pair  of  rolls  m  and  to  the  "first  quarter  of  the  sifter  o.  For  re- 
ducing the  low  grade  stock  and  bran  there  is  a  French  stone  mill  q  of  42  in. 
The  reduction  stock  passes  into  the  second  half  of  the  sifter  o2.  The 
duties  of  the  trays  sifter  o,  o1?  and  o2  are  appointed  as  follows  :  sieve 
No.  54  separates  the  tailings,  sieve  No.  15  and  No.  16  first  flour,  sieve 
No.  12  second  flour,  sieve  No.  10  third  flour,  sieve  No.  8  dunst. 

VI 

RYE  GRINDING 

As  in  wheat  grinding,  rye  grinding  may  be  divided  into  plain  and 
high  systems. 

Plain  Rye  Grinding  is  characterised  by  the  number  of  passages, 
which  varies  between  one  and  four.  If  the  milling  is  performed  on  rolls, 
they  are  all  corrugated,  while  for  a  more  rigorous  clean  up  of  the  bran 
there  is  placed  a  stone  mill  for  the  last  passage.  The  schemes  for  plain 
wheat  grinding  examined  may  be  adapted  for  rye  grinding  as  well,  with 
the  sole  difference  that  for  rye  grinding  there  have  to  be  used  rolls  300 
to  350  mm.  in  diameter,  as  owing  to  a  stronger  pressure  the  corrugations 
wear  more  rapidly  and  require  more  frequent  renewal, 


528  FLOUR   MILLING  [CHAP,  vin 

In  Russia  the  plain  rye  grinding  is  characterised,  in  addition,  by  the 
total  quantity  of  flour  obtained.  In  the  market  the  plain  ground  flour 
is  known  under  the  name  of  "  scoured  "  and  "  break  "  flour. 

The  "  scoured  "  flour  is  obtained  to  the  amount  of  95  per  cent,  of  the 
quantity  of  grain  fed  into  the  mill.  In  other  words  the  grain  is  ground 
to  flour  together  with  the  bran,  and  5  per  cent,  goes  to  the  offals  in  clean- 
ing. Two  or  three  passages  suffice  for  complete  reduction.  In  com- 
puting the  length  of  rolls  one  should  take  the  starting-point  of  its 
capacity  as  130  to  145  Ib.  to  1  cm.  per  day  (24  hours). 

The  "  break  "  flour  when  ground  in  three  to  four  passages,  the  large 
bran  being  sifted  away,  is  obtained  in  the  quantity  of  80  to  85  per  cent. 
One  ought  to  reckon  115  to  130  Ib.  per  day  to  1  cm.  of  rolls. 

The  high  rye  grinding  can  be  characterised  by  a  more  accurate  bolting 
of  the  flour,  and  the  number  of  passages  from  five  to  ten ;  the  crushing 
passage,  in  which  the  grain  is  broken  down  the  crease,  included.  The 
high  rye  grinding  is  designed  to  produce  several  (two  to  four)  grades  of 
flour,  or  one  higher  than  the  scoured  and  break  grades  of  flour. 

On  the  Russian  market  rye  flour  from  high  grinding  is  known  under 
the  appellation  of  dressed,  sifted,  and  bolted  flour.  Dressed  flour  is 
obtained  to  the  amount  of  70  to  72  per  cent.,  only  one  grade :  sifted  and 
bolted  flour  (two  to  four  grades)  yields  up  to  70  per  cent.  Bolted  flour 
of  the  best  grades  does  not  exceed  20  to  30  per  cent. 

In  very  rare  cases  in  Russia  purifiers  for  grading  the  middlings  ac- 
cording to  quality  are  adopted  in  bolted  rye  grinding.  In  other  countries 
the  use  of  purifiers  in  high  rye  grinding  is  not  to  be  met  with. 

Let  us  examine  some  of  the  characteristic  schemes  of  high  rye  grinding. 

High  Rye  Grinding. — The  common  plan  of  high  rye  grinding  prac- 
tised in  Russia  is  illustrated  in  Fig.  511.  The  mill  of  400  sacks  capacity 
per  day  operates  in  the 'south -western  region,  producing  the  best  flour. 

The  rye  brought  in  sacks  is  poured  out  in  front  of  the  silo  granary, 
whence  it  passes  through  the  elevator  to  the  automatic  scale,  hence  to 
the  preliminary  cleaning  apparatus,  and  then  through  the  elevator  and 
distributing  worm  into  the  bins. 

The  zigzag  separator  for  preliminary  cleaning  easily  cleans  the  rye, 
separating  away  mainly  the  coarse  impurities,  so  as  to  prevent  these 
admixtures  from  passing  together  with  the  rye  into  the  silo  and  stopping 
it  up.  The  dust  and  light  particles  of  impurities  sucked  in  by  the 
fan  in  the  cleaning  apparatus  go  to  the  pressure  filter,  and  are  thence 
automatically  sacked  off. 

From  the  silo  the  rye  passes  into  the  collecting  worm,  is  blended 


CHAI>.    VIII] 


FLOUR    MILLING 


529 


in  the  proportion  desired,  and,  mixed  in  this  manner,  goes  to  be  cleaned. 
Then  it  runs  through  the  automatic  scale,  aspirator,  magnet  apparatus, 
and  three  cockle  cylinders  connected  with  a  re -cockle  cylinder. 

Further,  it  passes  through  the  first  scouring  machine,  dust  reel-separa- 
tor,  second   scourer,   brush    machine    and   apparatus   and   worms    for 


FIG.  511. 

damping,  hence  it  goes  to  the  drying  chamber,  where  it  remains 
several  hours  to  allow  the  moisture  to  spread  well  in  the  bran.  The 
damping  apparatus  may  also  be  passed  over  or  not,  according  to  the 
quality  of  the  rye. 

All  the  machinery,  beginning  with  the  automatic  scale,  aspirator,  and 
cockle  cylinders,  &c.,  is  freed  of  dust  by  aspiration;    in  a  like  manner 

the  heavy  dust  is  separated  from  the  light. 

2  i . 


530  FLOUR   MILLING  [CHAP,  vm 

The  clean  rye  in  the  drying  chamber  passes  through  the  magnetic 
apparatus,  the  crushing  roll  800  x  350,  with  smooth  rolls  without  fluting, 
and  is  then  bolted  through  one-third  of  the  sifter. 

The  broken-down  rye  passes  through  an  apparatus  with  a  filter 
for  cleaning  the  break  chop  for  the  first  break.  The  break  is  repeated 
six  times. 

The  dimensions  of  the  mills  and  sifters  are  as  follows  : 


For  the  1st  break       .     2  pair  of  rolls  1000  x  350  mm.  and 

1  sifter  with  5  sieves. 

„       2nd      ,            .2 

800  x  350         „ 

I 

5        , 

„       3rd      , 

.     1 

1000x350         „ 

\ 

5 

»       4th      , 

.     1 

1000x350 

\ 

5 

,,       5th      , 

.     1 

1000x350.      „ 

\ 

5 

.1       6th      , 

.     1 

1000x350         „ 

\        • 

5 

For  reduction  of  semol.  1 

800  x  350         „ 

I 

5 

The  middlings  from  the  first,  second,  and  third  breaks  go  each  separ- 
ately to  a  pair  of  rolls  with  fine  corrugations  ;  from  the  fourth  break 
onwards  they  are  all  ground  together.  The  flour  mixes  together  with  the 
aid  of  collecting  worms  suspended  under  the  sifter,  and  all  the  grades 
can  be  prepared  for  sale.  The  yield  of  flour,  depending  on  the  quality 
of  the  rye,  is  68  to  72  per  cent. 

The  roller  mills,  as  well  as  the  elevators,  are  ventilated  by  a  powerful 
fan  communicating  with  a  suction  filter,  owing  to  which  the  heating  of 
the  running  parts  of  the  mills  or  the  sweating  of  the  machinery  in  general 
becomes  impossible. 

The  scheme  examined  is  defective  in  so  far  that  it  contains  no  grading 
of  middlings  according  to  quality,  which  is  a  characteristic  peculiar  to 
high  wheat  grinding. 

To  obtain  a  good  white  rye  meal  it  is  certainly  necessary  to  introduce 
purifiers.  In  Fig.  512  we  have  a  diagram  including  a  purifier  for  cleaning 
coarse  midds  from  the  first,  second,  and  third  breaks.  The  mill,  of  400 
sacks  capacity  per  day,  operates  in  the  government  of  Ekaterinoslav. 

The  coarse  midds  obtained  are  cleaned  on  the  purifier  and  subjected  to 
rebreak  on  passage  I  with  smooth  rolls,  the  corresponding  sifter  yielding 
the  dunst,  which  is  then  reduced  on  rolls  II.  The  flour  obtained  from 
this  dunst  to  the  quantity  of  6  to  8  per  cent,  is  the  best,  and  is  never 
mixed  with  the  best  kinds  of  break  flour.  The  flour  from  the  other 
smooth  rolls  is  blended  with  the  unif orm-quality  flour  from  the  corrugated 
rolls,  and  the  whole  is  divided  into  four  grades.  Flour  No.  0  from  the 
smooth  rolls  between  6  and  8  per  cent. ;  No.  1  smooth  rolls  together  with 
break  flour,  from  23  to  25  per  cent. ;  No.  2,  from  22  to  24  per  cent. ;  mill- 
stone flour  together  with  the  last  break,  from  10  to  12  per  cent.  The 


CHAP.    VIII] 


FLOUK   MILLING 


531 


total  amount  obtainable  with  an  accurate  scraping  is  between  65  and  69 
per  cent. 

The    employment    of    centrifugals  for   the   fifth    and   sixth   breaks 


FIG.  512. 

appears  to  be  useful,  as  the  rigorous  threshing   of   the  product  to  be 
sifted  allows  of  a  better  separation  of  the  flour  from  the  offal. 

The  defect  of  this  scheme  lies  in  the  absence  of  Hochschrot,  which  is 
very  necessary  for  rye,  as  it  is  generally  very  dirty  owing  to^the  dust  lying 
in  the  crease. 


532 


FLOUR   MILLING 


[CHAP,  vin 


On  the  other  hand,  it  must  be  acknowledged  that  the  adaptation  of 
a  millstone  for  cleaning  up  is  very  useful,  because  the  cleaning  up  of  the 
offals  is  performed  much  more  successfully  on  stones  than  on  corrugated 
rolls,  as  the  corrugations  become  rapidly  blunted  owing  to  strong 
pressure. 

German  Eye  Grinding .—The  rye-grinding  schemes  here  appended  are 
widely  practised  in  the  Chemnitz  district.  Let  us  successively  examine 
each  diagram. 

In  the  first  diagram  there  are  three  breaking  passages  through  corru- 
gated rolls,  the  first  pair  of  rolls  (800  mm.  X  300  mm.)  having  15  cor- 
rugations to  1  in.,  and  the  two  other  pairs  18  corrugations  to  1  in.  The 
differentials  of  the  corrugated  pairs  is  1:3.  Further,  there  are  two  pas- 
sages through  porcelain  rolls,  600  mm.  X  350  mm.  in  size,  and,  finally, 
two  stone  mills  1200  mm.  and  10€0  mm.  in  diameter  (Fig.  513). 

The   whole   grading   process   is  performed   on   hexagon  reels.     The 


FIG.  513. 

wire  sieves  of  the  first  reels  begin  with  No.  28  and  end  (cleaning  up  of 
integuments)  with  No.  36,  while  the  numbers  of  flour  sieves  of  the  flour- 
dressing  reels  have  as  their  utmost  limit  fourteen  (cleaning  up  the  offals 
and  third  break).  The  dimensions  of  the  reels  are  given  in  millimetres 
in  the  diagram  (length  and  diameter),  therefore  we  shall  not  repeat 
them  here. 

Let  us  watch  the  milling  process. 

After  cleaning,  the  grain  in  the  present  case  goes  to  the  first  break, 
though  often  enough  the  Germans  employ  in  the  first  passage  a  pair  of 
crushing  rolls,  the  purpose  of  which  is  to  divide  the  grain  down  the  crease. 
Up  to  the  third  break  the  tails  from  the  wire  and  flour  sieves  run  succes- 
sively to  the  second  and  third  break,  while  the  throughs  from  the  flour 
sieves  yield  the  final  product,  flour,  which  may  be  directed  to  flour- 
blenders.  But  the  tails  of  the  wire  sieve  in  the  reel  scalping  the  third 
break  go  to  be  finished  on  the  first  stone,  and  the  tails  of  the  flour 
reel  (silks  Nos.  13  and  14),  which  is  a  more  or  less  pure  dunst  and  fine 
middlings,  pass  to  porcelain  rolls.  The  tails  of  the  wire  sieves  in  the 


CHAP,  vmj 


FLOUR   MILLING 


533 


reels  after  both  roller  mills  with  porcelain  rolls,  and  from  the  flour  sieve 
of  the  second  passage  through  porcelain  rolls,  go  to  the  first  stone.  And, 
lastly,  we  have  two  passages  on  millstones,  the  aim  of  which  is  to  give 
a  final  clean  up  of  the  offal. 

The  capacity  of  such  a  mill  varies  between  120  and  160  sacks  with  a 
motor  of  60  H.P.,  the  grain  cleaning  included.     As  to  the  grades  of  flour, 


9000 


To  the  flour  blender. 

FlG.  514. 

they  may  be  combined  according  to  the  quality  to  three  or  four  brands. 
In  the  region  where  this  combined  grinding  on  corrugated  and  porcelain 
rolls  is  practised,  there  is  generally  obtained  45  to  50  per  cent,  of  the  so- 
called  "  white  "  flour,  No.  0. 

The  second  diagram  (Fig.  514)  differs  from  the  first  only  in  that  it 
has  an  extra  pair  of  porcelain  rolls.  Therefore,  owing  to  the  more 
accurate  reduction  of  dunst  and  middlings,  there  is  obtained  up  to  62 
per  cent,  of  flour  No.  0  and  No.  1,  which  is  also  classified  as  white 
flour. 

There  is  a  mill  in  Chemnitz  on  the  same  plan,  which  having  the  same 


To  the  flour  blender. 


FIG.  515. 

capacity,  requires  63  H.P.  for  the  milling  department  only,  i.e.  not 
reckoning  the  cleaning  of  grain.  Such  great  consumption  of  power 
can  be  explained  solely  by  the  considerable  demand  made  by  its  shafting, 
which  could  have  been  designed  more  accurately. 

Finally,  in  Fig.  515  we  have  a  third  milling  diagram  for  the  same 
capacity  per  day.  A  mill  with  grain  cleaning  needs  60  H.P.  This  type 
of  diagrams  approaches  the  old  French  milling  systems,  in  which  two- 
thirds  of  the  whole  process  in  high  grinding  was  performed  on  stone  mills. 


534  FLOUR   MILLING  [cHAt>.  vnt 

Improved  Scheme  of  German  Eye  Grinding. — In  the  newest  German 
rye  grinding  mills  the  hexagon  reels  are  totally  discarded,  and  the 
cleaning  up  of  the  offals  is  done  not  on  stones  but  on  rolls. 

In  Fig.  516  we  have  the  outline  of  an  inexpensive  semi-automatic 
mill,  which  shows  that  the  grain  goes  first  to  the  crushing  mill  with  smooth 
cast-iron  rolls,  where  it  is  broken  down  the  crease.  On  the  first  half  of 
the  small  sifter  A  the  blue  flour  is  pressed  through  No.  X  and  sacked  off, 
while  the  tails  pass  to  the  first  break  to  rolls  2.  The  product  of  the 
first  break  runs  to  the  first  quarter  of  the  sifter  B,  whence  the  flour  goes 
to  the  second  half  of  the  sifter  A,  which  does  controlling  duty  in  that 
part.  The  tails  of  the  first  quarter  of  the  sifter  B — the  break  stock, 
middlings,  and  dunst — runs  into  the  bin  //  and  awaits  its  turn  to  pass 
through  the  rolls  2.  After  the  second  passage  through  the  rolls  2,  the 
product  is  bolted  on  the  same  first  quarter  of  the  sifter,  the  tails  going  into 
bin  ///  for  a  third  passage — through  rolls  3.  The  sifting  of  the  third 
passage  is  performed  on  the  second  quarter  of  the  sifter,  dropping  the  tails 
into  the  bin  IV,  whence  the  product  goes  to  the  same  rolls  3  after  the 
passage  of  the  third  break. 

The  rolls  4  serve  also  for  two  passages,  the  product  of  which  is  bolted 
on  the  third  and  fourth  quarters  of  the  sifter  B.  All  'the  flour  out  of 
sifter  B  is  directed  to  the  controlling  half  of  the  sifter  A.  In  this  way 
one  may  obtain  several  grades  of  flour  by  distributing  them  among  the 
bins,  or,  if  they  are  run  together  in  the  blender,  one  grade. 

The  rolls  5  serve  for  cleaning  up  the  bran.  On  these  rolls  large  as  well 
as  fine  bran  may  be  obtained,  for  which  purpose  there  are  three  bins,  VII, 
VIII,  and  IX,  over  them. 

From  the  controlling  sifter  the  dunst  is  sent  to  the  first  quarter  of 
the  sifter  B,  where  the  flour  fallen  into  the  tails  is  separated  from  it, 
after  which,  together  with  the  dunst  and  middlings,  from  the  first  break 
it  goes  to  the  second  break. 

With  the  same  machinery  milling  can  be  practised  according  to  a  more 
abridged  scheme  with  four  passages  after  the  crushing  mill. 

Then  there  are  three  breaking  passages  and  a  fourth  for  cleaning  up 
the  bran. 

All  the  roller  mills,  except  the  Hochschrot,  are  ventilated  by  means  of 
fan  C  and  a  suction  filter  D. 

Thus,  the  whole  milling  plant  consists  of  a  crushing  mill,  two  four- 
roller  mills  with  corrugated  rolls,  two  sifters  for  two  and  four  sections,  a 
filter,  and  a  fan.  A  flour-blender,  not  given  in  the  diagram,  is  likewise 
indispensable. 


CHAP.    VIII  ] 


FLOUR   MILLING 


535 


Bran. 


FIG    516. 


536 


FLOUR   MILLING 


[CHAP,  vin 


VII 
MAIZE  GRINDING 

In  Russia  there  is  only  known  a  primitive  system  of  maize 
grinding  with  a  single  passage  through  a  millstone  set  without  sifting 
away  the  offals.  In  the  south  of  Russia,  however,  especially  in  Bessa- 
rabia, the  question  of  rational  grinding  is  awaiting  a  solution.  For  this 
reason  we  append  a  diagram  of  maize  grinding,  accepted  in  America  and 
partly  in  Hungary. 

The  maize  (Fig.  517)  is  poured  into  the  storing  bin  a,  whence  the 


FIG.  517. 

elevator  carries  it  to  the  separator  b  with  a  sieve.  The  sieve  separates 
the  large  impurities,  such  as  stones,  clods  of  earth,  &c. 

By  aspiration  in  the  separator  the  maize  is  freed  of  straw,  dust,  &c., 
and  this  light  refuse  collects  in  the  dust  chamber. 

The  cleaned  maize  is  conveyed  by  the  elevator  to  the  bin  c  over  the 
roller  mill. 

The  first  break  is  done  on  one  pair  of  rolls,  and  the  product  is 
crushed,  and  then  goes  to  be  graded  in  the  first  section  of  the  sifter  /. 
From  the  sifter  the  break  middlings  are  sent  to  the  bin  e  to  be  passed 
through  the  second  pair  of  rolls,  where  the  break  is  kept  very  low.  After 
these  rolls  the  product  is  graded  in  the  second  section  of  the  sifter.  The 
flow  of  the  break  middlings  is  altered  in  a  closed  chamber  so  as  to  pass 
through  the  first  break  rolls. 


CHAP.    Vlll] 


FLOUR   MILLING 


537 


53$  FLOUR   MILLING  [CHAP,  vnl 

Thus,  the  product  obtained  here  is  sacked  off,  which  allows  of  making 
four  breaking  passages. 

In  the  breaking  process  most  attention  is  paid  to  the  production 
of  semolina  with  the  least  produce  of  break  flour,  i.e.  as  high  a  grinding 
as  possible  is  practised.  The  flour  from  the  sifters  is  sacked  off,  while  the 
middlings,  the  fine  as  well  as  the  large,  go  to  a  new  purifier  with  six 
divisions,  where  the  product  is  graded  according  to  quality.  The  pure 
middlings  are  packed,  and  the  offals  are  sent  to  the  millstone,  where  they 
are  reduced,  and  then  go  to  be  graded  in  the  third  section  of  the  sifter. 
The  purifier  fan  drives  the  extracted  bran  down  a  spout  into  the  dust 
collector  h,  whence  it  goes  to  the  sack. 

The  middlings  are  used  for  baking  bread,  the  remaining  products, 
such  as  flour  and  other  offals,  serve  as  feed  for  cattle. 

The  arrangement  of  the  machines  is  such  that  by  increasing  their 
number  the  milling  process  can  be  made  quite  automatic,  which  affords 
economy  in  working  power. 

Figs.  518  and  519  illustrate  a  cross  and  a  longitudinal  section  of  a 
mill  for  reducing  40  sacks  of  maize  per  day.  This  mill  is  operated  by 
means  of  a  20  H. P.  benzine  motor  with  a  belt  drive  to  the  main  shafting. 

On  the  first  floor  of  the  mill  are  stationed:  storing  bin  (a,  04),  elevator 
bottoms,  the  main  shafting,  a  four-roller  mill  220x475  mm.,  and  a 
36-in.  stone  mill.  In  the  garret  apartment  there  are  set :  a  separator  6, 
a  middlings  grading  plansifter  /,  a  group  purifier  d  with  six  sections,  a 
fan  g,  a  filter  dust -collector  h,  the  elevator  heads,  and  a  shaft  receiving 
its  motion  from  the  main  shafting  and  transmitting  it  to  all  machines 
on  that  floor. 


VIII 

SCHEME  or  OATMEAL  GRINDING 

Oatmeal  manufacture  is  one  of  the  branches  of  a  widely  developed 
industry — the  preparation  of  cereal  foods.  The  corn,  cereal,  or  break- 
fast foods  are  prepared  of  the  grain  of  maize,  oats,  wheat,  sometimes 
barley  freed  of  the  skin,  crushed  to  a  thin  loaf,  roasted  or  dried.  They 
are  used  in  almost  every  family  for  breakfast  with  sugar  and  milk — the 
maize  and  wheat  dry,  and  the  oats  boiled. 

In  Russia  oatmeal  is  known  under  the  name  of  American  flakes  ("  Her- 
cules "),  which  have  nothing  in  common  with  American  "  Quaker  Oats  " 
neither  in  quality  nor  in  outward  appearance. 


FLOUR   MILLING 


530 


CHAP.    VIII] 

Since  crushed  oats  are  sold  by  American  manufacturers  wholesale 
in  boxes  at  5d.  to  Id.  per  lb.,  in  barrels  at  3d.  to  4d.,  and  all  the 
offals  are  sold  as  cattle  feed,  no  less  than  £1  to  £1,  4s.  is  obtained 
per  1  cwt.  of  oats  after  the  product  is  ready. 


That  proves  that  the  manufacture  is  profitable,  and  one  ought  to  be- 
come acquainted  with  it. 

In  Fig.  520  is  shown  the  outline  of  a  mill  designed  for  a  capacity  of 
20  sacks  per  day. 


540  FLOUR   MILLING  [CHAP,  vm 

First  of  all,  the  grain  goes  to  the  separator  No.  1  with  two  sieves. 
The  first  sieve  bolts  the  oats  separating  large  impurities,  on  the  second 
fine  impurities  and  dust  are  removed.  The  fan  carries  away  the  light 
dirt  and  poor  grains.  From  here  the  stock  goes  to  the  grading  separator 
No.  2,  which  separates  away  the  small  oats  useless  for  production.  On 
some  of  the  mills  the  cleaning  is  performed  with  the  aid  of  flat  sieves 
with  oblong  perforations  and  an  automatic  brush  for  cleaning,  or  by  means 
of  a  grading  reel-separator  No.  3. 

These  machines  extract  all  fine  impurities  and  sort  away  the  large, 
heavy  oats. 

After  a  careful  cleaning  and  sorting  away  of  the  heavy  grain  equal 
in  size,  it  is  dried  in  the  dryer  No.  4  if  very  damp  to  facilitate  the  hulling, 
and  at  the  same  time  slightly  roasted  to  give  it  a  flavour. 

The  dryer  generally  employed  is  a  metal  pan  for  treating  twenty 
barrels  per  day.  The  pan  is  10 1  ft.  in  diameter  and  up  to  9  in.  deep. 
It  is  cemented  into  the  stove  which  is  arranged  under  it.  To  prevent  the 
grain  from  getting  burned,  it  is  stirred  the  whole  time.  One  load  of  oats 
of  some  8  cwt.  is  dried  in  three  hours.  The  stove  is  built  of  brick ; 
the  pan  is  set  on  it  with  the  aid  of  flanges  in  such  wise  that  its  bottom  and 
sides  are  subjected  to  the  effect  of  the  hot  air. 

Well  dried  and  roasted  oats  are  very  brittle  and  friable.  They  pass 
in  succession  through  scouring  grinders  of  artificial  stone. 

After  each  millstone  passage  (Nos.  5,  6  and  7)  the  grain  goes  to  the 
separator  with  a  sieve  (No.  8,  shell  remover),  the  tails  of  which  are  guided 
to  the  stones,  and  the  last  one  of  them  polishes  the  grain.  After  the  stone 
No.  7  the  grain  goes  to  be  finally  freed  of  the  integumental  dust  and  the 
partly  cut  hulls,  which  is  performed  on  the  separator  No.  9. 

Now  the  grain  is  ready  to  be  steamed  and  crushed.  The  steaming 
machine  here  is  similar  to  the  one  used  for  feed.  It  works  unintermit- 
tently.  In  America  copper  steaming  cylinders  of  continuous  action  are 
employed.  The  flow  of  grain  into  the  hopper  at  the  top  is  regulated, 
because  with  a  change  in  the  height  of  the  column  of  grain  the  steam 
introduced  from  below  into  the  steam  pipe  will  burst  through  the  grain 
and  steam  it  insufficiently.  The  grain  in  the  steaming  machine  is  con- 
tinually stirred  with  a  stirrer.  The  steamed  grain  passes  to  the  rolls. 

The  steaming  machine,  the  rolls,  and  the  dryer  are  combined  into  one 
machine,  No.  10,  which  economises  space. 

The  process  of  crushing  heats  the  product,  and  on  leaving  the  rolls 
it  is  spread  out  in  a  thin  layer  in  the  cooler.  This  cooling  dries  it 
sufficiently  for  immediate  packing  in  boxes  or  barrels. 


CHAP,  vin]  FLOUR    MILLING  541 

In  case  the  cooling  alone  appears  to  be  insufficient  to  dry  the  oat- 
meal the  steam  is  let  into  the  pipes  of  the  refrigerator  and  thus  a  final 
drying  is  attained. 


IX 

QUANTITY  or  INTERMEDIATE  PRODUCTS  AND  THE  CALCULATION 
OF  CORRESPONDING  MACHINES 

In  computing  the  number  of  corrugations  and  the  capacity  of  the 
break  and  rebreak  mills  we  availed  ourselves  of  the  practical  data, 
taking  the  average  quantities  of  break  and  rebreak  middlings.  Now 
after  we  have  sufficiently  become  acquainted  with  the  general  scheme 
of  milling,  we  may  define  the  dimensions  of  the  roller  mills  for  rebreaking 
the  semolina,  for  the  reduction  of  middlings,  and  the  cleaning  up  of  the 
offals  in  accordance  with  the  quantity  of  the  intermediate  products. 

In  the  plans  examined  we  did  not  occupy  ourselves  with  the  estima- 
tion of  the  dimensions  of  the  machines,  acquainting  ourselves  only  with 
the  existing  types  of  milling  processes.  Therefore  we  must  now,  at  once, 
point  out  that  the  dimensions  of  the  machines  given  in  the  appended 
milling  diagrams  are  far  from  the  correct  calculation,  especially  as 
regards  the  dimensions  of  the  roller  mills. 

It  must  be  noted  that  for  break  as  well  as  for  reduction  roller  mills, 
practice  often  establishes  one  and  the  same  size  of  rolls,  having  in  view 
only  the  convenience  of  erection  and  economic  considerations.  These 
considerations,  however,  are  incorrect  and  injurious  to  the  business.  In 
fact,  if  at  a  mill  with  a  certain  capacity  one  were  to  take  rolls  of  a  size 
normal  for  the  third  break,  and  for  all  other  passages  establish  the  same 
size,  then,  owing  to  the  absence  of  proportion  of  the  capacity  of  the  mills 
with  different  passages,  these  mills  will  be  either  overloaded  or  under- 
loaded. This  is  observed  in  fact  in  the  mills  of  Russia  and  abroad,  their 
builders  not  having  proceeded  on  the  basis  of  a  correct  calculation  of 
the  machinery. 

Quantity  of  Intermediate  Products. — We  shall  start  with  the  more 
complex  milling  process — the  high  grinding.  In  F.  Baumgartner  and 
L.  Graf's  book  there  are  given  tables  of  the  quantity  of  intermediate 
products,  determined,  according  to  the  authors'  words,  from  the  results  of 
detailed  investigations  of  the  milling  processes  in  different  years.  The 
wheat,  which  was  treated  at  the  mills  subjected  to  investigation,  was 
the  ordinary  market  grade. 

*  Pp.  229-233  and  305-312, 


542 


FLOUR    MILLING 


[CHAP,  vni 


Thus,  the  tables  by  Baumgartner  and  Graf  hereto  appended  give  us 
the  average  quantities  of  the  intermediate  products  for  high  wheat  grind- 
ing, the  relation  of  the  soft  and  the  hard  wheat  having  been  1:2. 
Approximately  the  reverse  relation  on  the  average  is  observed  in  Russia, 
where  60  to  70  per  cent,  of  soft  and  40  to  30  per  cent,  of  hard  wheat  is 
generally  ground. 

In  this  way,  with  two-thirds  of  hard  wheat  and  one-third  of  soft 
after  cleaning  there  was  obtained  96  per  cent,  of  grain  ready  for  milling, 
so  that  the  average  losses  in  cleaning  were  4  per  cent. 

After  eight  breaking  passages  and  one  rebreak  the  results  of  Table 
LIII  were  obtained. 

TABLE    LIII 

BREAKING  PROCESS 


BREAK. 

Fed  in 
100  per 
Cent. 

BrGrkadFeOUr      !     Dun.t  Grade. 

Middlings 
Grade. 

Rebreak 
Middlings. 

Bran. 

Loss. 

1. 

2.     i    3.     I    1.         2.         3. 

1.        2. 

3. 

1st  break 
2nd     „ 
3rd     „ 
4th     „ 
5th     „ 
6th     „ 
7th     „ 
8th     „ 

96-0 
94-75 
87-0 
57-0 
29-0 
17-0 
13-0 
9-5 

2-0 
2'5 
2-0 

.   O25 
...  025 

(< 

i'-b  ;;; 

...  |  1-6 

...  :  i-o 

i 

2V0 
2-5 
2-0 

...  io-25 
0-5     ... 

i'-b   '.'.I 

...      2-0 
...      2-0 

!.'.'    6-b 

24-0  i  ... 
21-0  1  ... 
...     7'0 

0'25 
2-0 

0-5 
1-0 
2-0 
2-0 
1-0 

... 

•• 

7-25 



Rebreak 

6-5 

O-7fS 

0-25 

1         i 

i 

Total     . 

409-75  10-5  per  cent. 

13  per  cent.    60-25  per  cent. 

6'5  % 

7-25% 

0-25 

Thus,  there  were  obtained  10 '5  per  cent,  of  break  flour,  13  per  cent, 
of  dunst,  60-25  per  cent,  of  middlings,  7-25  per  cent,  of  large  bran,  and 
0-25  per  cent.  loss.  One  must  bear  in  mind,  however,  that  the  grades 
(1,2,  and  3)  of  break  flour  do  not  correspond  in  quality  to  the  same  grades 
of  middlings  and  dunst.  By  denoting  the  break  stock  by  the  three 
grades,  it  is  meant  that  each  group  of  product  is  divided  into  three  cate- 
gories, according  to  quality,  which  is  different  in  the  flour,  the  dunst, 
and  the  middlings. 

The  process  of  grading  the  middlings  and  dunst  according  to  quality, 
as  we  know  already,  is  of  very  great  importance,  since  from  the  moment 
the  middlings  are  graded  the  grades  and  the  quality  of  flour  are  computed, 


CHAP.    VIII] 


FLOUR    MILLING 


543 


w    h 

^      o 


H      5 


•8801 


e 

Q 


8 

Us 


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«   i  £ 


544 


FLOUR   MILLING 


[CHAP,  vin 


Each  break  gives  us  a  certain  quantity  of  product,  approximately 
uniform  in  quality.  The  products  of  the  second,  third  and  fourth  breaks 
are  the  most  closely  related  in  quality. 

In  Table  LIV  we  have  the  results  of  grading  the  middlings  and 
dunst  according  to  quality. 

From  the  table  it  may  be  seen  that  the  total  quantity  of  purified 
middlings  and  dunst  obtained  was  about  75  per  cent.,  2J  per  cent,  being 
reckoned  to  the  losses  in  dunst  and  offals. 

The  further  process,  rebreak  of  middlings  and  large  dunst  (in  Russia 
this  dunst — Pohlgries — corresponds  to  middlings  of  the  utmost  fineness) 
is  clear  by  Table  LV. 

TABLE    LV 

REBREAK  OF  MIDDLINGS  (AUFLOSUNG) 


Rebreak  of  Middlings  (polishing) 

100 
PerCent. 

Flour  per  Grade. 

Dunst  per  Grade. 

1 

PQ 

1. 

2. 

3. 

00. 

0.     !     1. 

2.         3. 

1st    rebreak    (best    mid-  ) 
dlings  —  Auszugsgries)  } 

25 

1 

... 

10 

13 

... 

... 

1 

... 

2nd   rebreak   (2nd  grade  > 
Mundgries)  .         .         .  ) 

21  +  1 

1 

... 

... 

... 

10     9£ 

... 

H 

... 

3rd     rebreak     (Semmel-  > 
gries)    .         .         .     .    .) 

Hf  +  H 

1 

10 

... 

... 

at 

... 

4th  rebreak  (Pohlgries)  . 

6|  +  2| 

... 

1 

... 

... 

... 

5 

2| 

... 

5th  rebreak 

if 

... 

... 

t 

... 

t 

... 

! 

... 

6th  —  cleaning  up  the  bran 

1 

... 

... 

* 

... 

...       J 

... 

I 

Total     .... 

... 

3 

1 

t 

10 

23 

25| 

t 

In  this  way,  as  we  see,  three  grades  of  flour  and  three  grades  of  dunst 
have  been  obtained.  In  the  Russian  granular  grinding  the  00,  0,  and  1 
grades  of  dunst  could  be  regarded  as  a  ready  product — granular  flour. 
But  the  Germans  produce  almost  exclusively  fine  flour,1  and  therefore 
dunst  00,  0,  and  1  is  subjected  to  further  reduction.  Table  LVI 
gives  us  a  table  of  dunst  reduction  and  the  extraction  of  blue 
flour. 

Table  LVI   shows  the  final  result  of  milling.     There  are  obtained 

1  Only  quite  recently  the  preparation  of  granular  flour  has  begun  here  and  there  in  Germany. 


CHAP.    VIIl] 


FLOUR   MILLING 


545 


s  5 

59    I! 


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S         s  •*•«•  V*  --  r.  .-*-''•  :':s  -  T:-.S 

^                               s 

1 

*c«    » 
.._,     O     t-t 

0    a 

.^3* 
115 

|g£ 

C^       lJ 

^.TJTJ 
c8    G   C 

||.S 

1 

'o 

4^ 

3 

1 
£ 

546 


FLOUR   MILLING 


[CHAP,  vm 


eight  grades  of  flour,  beginning  with  No.  00  and  ending  with  No.  6,  the 
sum  total  being  78  per  cent. ;  there  is  16 J  per  cent,  of  bran  of  all  kinds, 
and  the  losses  amount  to  1|  per  cent. 

In  this  manner  the  whole  process  of  high  German  grinding 
requires  no  less  than  twenty-three  passages.  If  the  Hochschrot 
and  yet  another  rebreaking  passage  are  to  be  set  in  addition, 
which  is  very  useful,  the  total  number  of  passages  will  be 
twenty-five. 

Dimensions  of  the  Machines. — As  regards  the  number  and  dimensions 
of  the  bolting  machines  and  purifiers,  they  may  be  easily  selected  in 
accordance  with  the  quantity  of  intermediate  products  according  to 
the  tables  of  capacity  we  gave  on  pp.  388-390  and  421.  For  the 
rebreak  (sizing)  of  middlings,  reduction  of  dunst,  and  finishing  of  offals 
we  offer  the  following  Table  LVII. 


TABLE    LVII 

REBREAK  OF  MIDDLINGS,  REDUCTION  OF  DUNST,  AND  CLEANING 

UP  OFFALS 


Passages  in  Order  of 
Sequence. 

Length  of  Eolls  in  mm.  to  One  Sack  per  Twenty-Four  Hours. 

Porcelain  Rolls. 

Cast-iron  Rolls. 

Reduction  of  Dunst 
—Cast-iron  Rolls. 

Scraping  of  Hulls 
—Cast-iron  Rolls. 

1st  rebreak    . 
2nd      „ 
3rd       „ 

4th       „ 
5th       „ 

1-30-1-50 
2-25-2-65 
2-25-2-65 
1-30-1-50 
1-10-1-35 

1-40-1-65 
2-50-2-85 
2-50-2-85 
1-40-1-65 
1-30-1-50 

1-90-2-10 

1-30-1-90 

The  differential  of  the  rolls  for  rebreak  of  middlings  should  be 
taken  as  4 :  5  with  the  number  of  revolutions  for  the  fast  roll  200 
to  210  ;  for  reduction  rolls,  the  fast  roll  running  at  230  to  235  re- 
volutions, the  differential  is  5:6;  and  for  rolls  cleaning  up  the 
offals,  the  fast  roll  making  250  revolutions,  the  differential  to  be  taken 
is  4  :  5. 

Kettenbach  gives  the  following  table  of  dimensions  of  rolls 
for  break,  rebreak  of  middlings  (Auflosung),  and  the  reduction 
of  dunst  in  different  grinding  systems  for  a  50,000  klg.  capacity 
(Table  LVIII). 


CHAP.    VIII] 


FLOUR   MILLING 
TABLE    LVIII 


547 


System  of  Grinding. 

Break. 

Rebreak  of  Middlings. 

Reduction  of  Dunst. 

Number  of 
Passages. 

Length  of 
Rolls. 

Number  of 
Passages. 

Length  of 
Rolls. 

Number  of 
Passages. 

Length  of 
Rolls. 

High     ...     .     . 

6 

mm. 

9000 

5 

mm. 

5000 

8 

mm. 

7750 

Semi-high     . 

4 

7500 

4 

4500 

6 

6000 

English  .... 

4 

1000 

4 

6500 

8 

7500 

The  ordinary  high  German  grinding,  i.e.  with  six  breaking  passages, 
is  given  out  here. 

It  must  be  noted  that  Kettenbach  gives  a  capacity  considerably  below 
the  established  norm.  According  to  our  observations,  for  high  grinding 
the  following  general  working  length  of  rolls  may  be  given  (Table  LIX). 

TABLE    LIX 


Process. 

Number  of 
Passages. 

Length  of  Rolls 
in  mm. 

Break                 ....      .      . 

8 

8600 

Rebreak  of  middlings       .      ...     > 

5 

4500 

Reduction  of  middlings  and  dunst   . 

9 

6750 

RUSSIAN  GRINDING 

As  was  mentioned  before.  Russian  systems  have  been  to  a  large  extent 
borrowed  from  the  Hungarians  and  Germans.  The  material  difference 
between  Russian  high  grinding  and  the  Austro-German  consists  in  the  fact 
that  the  dunst  Nos.  00,  0,  and  1  corresponds  approximately  to  the  Russian 
coarse  flour  (granular),  and  is  taken  as  a  finished  product.  The  Russian 
system  not  yet  being  stereotyped,  the  percentage  of  yields  will  also  vary. 

The  Siberian  system  is  also  very  characteristic,  the  peculiarity  of 
which  consists  in  that  there  are  only  four,  seldom  five,  grades  of  flour 
made. 


548 


FLOUR   MILLING 


[CHAP,  vin 


To  illustrate  the  Russian  system  we  shall  give  the  percentages 
of  the  yield  of  flour  in  different  parts  of  the  country.  Great  inconvenience 
is  offered  to  the  comparison  of  the  qualities  of  the  grades  of  flour  by  the 
absence  of  uniformity  in  the  brands.  For  this  reason,  when  studying 
these  tables  one  must  compare  not  the  brands  or  Nos.,  but  the  percentage 
of  flour  in  connection  with  the  general  table. 

VOLGA  REGION 
Hard  and  soft  wheats  were  milled.     The  data  refer  to  1910  and  1911. 

Mixture — Hard  Wheat,  40  per  cent. 

Soft  Wheat,  60  per  cent. 
Grade.  Yield  in  100  per  Cent. 

0  blue     .  .  .  .      ;  .  11-00 

1st  blue  .  /  V  .  ^:  .     7-00 

2nd   „     .  ...  .      ;  .  14-00 

2nd  red  .-  ,  .  .  -'.',  .     4-75 

1st  black  .  .  .  ;.'••  .  14-00 

2nd  black  .  ^.-;      .  .     6-00 

3rd  grade  .  .  .      .  .  12-00 

4th      „  .'  .  .      .  .     8-00 
5th                                                2-5 


Mixture—  Hard  Wheat  58 

per  cent. 

Soft  Wheat  42  per  cent.  ( 

Russian). 

Grade.                                      Yield  in  100  per  Cent. 

1st  blue  

.   23-00 

1st  red    . 

.      4-00 

2nd  blue       .... 

.    18-75 

2nd  red  

.      8-00 

1st  black      .... 

.    10-00 

2nd  black     

.      3-00 

3rd  grade     .... 

.     5-75 

4th      „          .... 

.      6-75 

5th     „    

.      3-00 

Total  amount  of  flour 

.    82-25 

Offal      .... 

.    16-75 

Losses  .... 

.      1-00 

Total  .      .      . 

100-00 

Total  amount  of  flour 
Offal     .      .      . 
Losses  . 


Total 


80-25 

18-60 

1-15 

lOO'OO 


SOUTHERN  REGION 

The  southern  region  offers  a  great  variety  of  grades  and  yields  of  flour, 
prepared  mostly  from  local  wheat.  The  data  given  below  were  obtained 
at  the  Ekaterinoslav  District  Farm  and  Industrial  Exhibition,  1910, 

WHEAT  MILL,  EKATERINOSLAV 

1909 
Granular  flour  No.  00  (including  semolina,  granular 

flour  No.  0000  and  No.  000)          .          .          ,     22  per 
Soft  flour  No.  0  8 

»     No.  1          .          .          .          .          .          .11 

»        NO-   2  .  .          '  -;•'.  .  .  .         10 

„     No.  II        .        ...  v      .          .          .          .        8 

»  '  »    No.  3     ; "...    ';,/_  .:--:     ...      8 

„       „     No.  Ill      .       -~;          .          .          .          ,       6 

„       „     No.  IV  felf;  '   .:     ';,--  i 

Total  amount  of  flour        r  .          .          ,74  per 


cent. 


cent, 


CHAP,  viii]  FLOUR   MILLING  549 

WHEAT  MILL,  EKATERINOSLAV — continued 
1909 

Fine  offal   .          .          ....          .  2  per  cent. 

Coarse  sharps  and  small  bran        .          .          .14         „ 
Broad  bran  4 


Total  amount  of  offal     .          .          .     20  per  cent. 

Screenings  from  the  grain-cleaning  department  (wild 

oats,  barley,  cockle,  and  scouring  dust)        .       6         ,, 

Thus  the  mill  yields  74  per  cent,  of  flour,  20  per  cent,  of  offal,  and  6 
per  cent,  of  losses  in  the  grain-cleaning  department. 


1910 

Granular  flour  No.  00  (including  semolina,  No.  0000 

and  No.  000)  .          .          .          .          .          .20  per  cent 

Soft  flour  No.  0 8 

„       „     No.  1  .          .          .          .          .          .     11 

„       „     No.  2 9 

„       „     No.  II  .        ...        .          .          .          .       8 

„       „     No.  3  .          .          .          .          .          .       8 

„       „     No.  Ill  ...          .         .         .7         „ 

No.  IV  1 


Total  amount  of  flour        .          .          ,          .          .72  per  cent. 

Fine  offal 2 

Sharps  and  small  bran         .          .          .          .17         „ 
Broad  bran  3 


Total  amount  of  bran    .  .     22  per  cent. 

Loss   in  the   grain-cleaning   department    .          .       6         ,, 

The  milling  process  of  1910  is  the  same  as  that  of  1909 ;  the  wheat  is 
dryer,  and  therefore  the  quality  of  the  flour  is  better,  but  the  yield  of  the 
first  grade  and  several  other  grades  is  less.  The  total  percentage  of 
yields  is  smaller,  but  there  is  more  fine  bran  and  less  large  bran,  as 
may  be  seen  in  the  table.  This  is  explained  by  easy  abrasion  of  the 
bran  coats  on  dry  wheat.  Therefore  it  would  be  useful  to  give  a  stronger 
dampening. 

The  wheat  is  very  dirty,  therefore  the  losses  of  the  grain-cleaning 
department  come  up  to  6  per  cent. 


550 


FLOUR   MILLING 


[CHAP.    VIII 


WHEAT  MILL,  ALEXANDROVSK 
I.  High  Wheat  Grinding 

Granular  flour  No.  0000  .  .  0'54  per  cent. 

„      No.    000  .  ,  3-39  „ 

Black           .     No.      00  .  .  13-91 

Red    .          ,     No.      00  .  .  8-39  „ 

„       .        Y    No.        0  .  .  8-02 

„       ;         .     No.        1  .  .  11-55  „ 

„  '  -  .      ••:•;•    No.        2  .  .  9-67  „ 

„       .          .     No.        3  .  .  7-18  „ 

„      V         ;     No.         4  .  5-62  » 

„      Y         .     No.         5  .  .  4-04  „ 

Large  bran      ....  2-15  ,, 

Fine       „          .          .  .  .  20-47 

Broken  grain  arid  small  wheat  .  2-11  ,, 

Wild  oats  and  barley  .  .1-00  ,, 

Scouring  dust            .  .  ..1-9.6  ,, 


72-31  per  cent,  of  flour. 


/ 

h22-62  percent,  of  bran 

>5'07  per  cent,  of  offal. 


Flour  .  No.  0000 
No.  000 

"  Hercules  "  No.  0 
No.  4 
No.  5 

Large  bran 

Jine       „         .          . 

Dunst     .         _.          . 

Scouring  dust 

Broken  grain  . 

Small  wheat    . 

Weeds 


II.  Soft  Wheat  Grinding 
(Export  flour) 

6-6    per  cent. 

•  9'4ll  " 

.   48-5)|     „ 
•     4-8^       „ 

•  I    '  -*-     *  5  ? 

.     2-6 
.    17-5 

.      4-8 

.      1-4 

.     0-8 

1-4 

0-8 


70-7  per  cent  of  flour. 


24-9  per  cent,  of  bran. 


4-4  per  cent,  of  offals. 


Total  100  per  cent. 


Flour  No.  00  . 
„      No.    0  . 

„      No.    3  . 
„      No.    4  . 

No.     5   . 


III.  Soft  Grinding 
(Without  export  flour) 

.   53-88  per  cent." 
.  '       .      1-90       „ 

.-        .      5-80        „ 
.    •       .      4-80 
3-70 


70-08  per  cent,  of  flour. 


4-80  per  cent,  of  offals. 


CHAP,  vm]  FLOUR   MILLING  551 

III.  Soft  Grinding — continued 

Large  bran      .          .          .        ..     2-72  per  cent. ) 

Fine       „         ,          .          .          .    17-60       „         [25-12  per  cent,  of  bran, 

Dunst     .          .          .  .  .  4*80       ,, 

Weeds    .          .  •".""  .  .  0-90 

Small  wheat    .          .  .  .  1-50 

Scouring  dust           .  •:  >  .  1-40       ,, 

Broken  grain  .          .  .  .  1-00       , , 

The  above  data  from  Niebuhr's  mill  are  the  average  yields  for  the 
space  of  ten  years  (from  1900  to  1910).  The  yields  in  the  Table  II  are 
obtained  from  mills  adapted  almost  exclusively  for  export  into  ports  on 
the  Black  and  Mediterranean  Seas. 

WHEAT  MILL,  EKATEEINOSLAV 

The  mill  yields  nine  grades  of  flour,  manufacturing  brands  which  go 
to  the  London  market.  The  average  yields  per  grade  are  represented 
according  to  the  data  of  1909. 

Percentage  of  Yield. 

Granular  flour  No.  000          .  .          .          .          .     4-37  per  cent. 

Soft  flour          No.    00}forexport          .          .          .          .20,9       ;; 

No.  1  .          .          .          .          .          -  9-54  „ 

No.  2  .          :          .   '       .          .          .  9-68  „ 

No.  3  .          .          .          .          .          -  9-47  „ 

No.  4  .          .          .          .          .          .  6-61  „ 

No.  5  ......  5-76  „ 

No.  6  .  0-92  „ 


Total  amount  of  flour       .  .   76-51  per  cent. 

Fine  offal.  .          .....  .     9-29       „ 

Large  bran          ...  •    11*24       ,, 

Total  amount  of  produce  .          .          .   97-04  per  cent. 

Screenings  loss    .  .     2-96       ,, 

Total        .          .          .      |  .          ..  100-00  per  cent. 

WHEAT  MILL,  EKATERINOSLAV 

Before  packing  the  flour  is  graded,  and  to  flour  No.  1  is  added  the 
flour  from  the  third  break,  to  flour  No.  2  that  of  the  fourth  break,  to 
No.  3  of  the  second  break,  to  No.  4  of  the  second  and  sixth  breaks,  and  to 
No.  H4  the  flour  from  the  first,  sixth,  and  seventh  breaks. 


652  FLOUR   MILLING  [CHAP,  vni 

The  yields  of  flour  in  percentages  are  given  in  the  following  table  : 

.          .          .          .          .6    per  cent. 


Flour,  brand  000 

00 

0 

1 
2 
3 
4 
H4 


Finest  offals 
Large  bran 
Fine  bran 


Wild  oats 
Weeds  . 
White  dust 
Dark  dust 


Total  amount  of  flour 


Total  amount  of  offal 


Hi 

12 

10J 

7 

76~ 

3J 
2f 

11* 

17 

II 


Total  amount  of  screenings 
Total 


2f         „ 
7|         „ 
100J  per  cent. 


Instead  of  the  ordinary  result  of  exactly  100  per  cent,  here  we  have 
100-5  per  cent.  This  means  that  the  total  weight  in  a  correct  calculation 
increases  on  account  of  the  dampening  of  the  wheat,  which  absorbs  the 

moisture. 

TABLE  LX 

WHEAT  MILL,  MAKIOOPOL 


Flour  Grades 

Belotoorka. 

50  per  cent.  Belotoorka  and 
50  per  cent.  Banatka. 

1st  grade 

6-50  per  cent. 

15-00  per  cent. 

2nd     „ 

6-50         „ 

10-00 

3rd     „       :  .          .          .' 

6-50 

12-50 

4th     „         .          ,          , 

28-00 

11-25 

5th     „          .    ,      , 

11-25 

11-25 

6th     „         . 

10-50 

'10-00 

7th     „ 

6-50 

6-50 

Total 

75  «7  5  per  cent. 

76  -60  per  cent. 

Sharps 

5-50  per  cent. 

5-50  per  cent. 

Fine  bran    .          , 

7-75 

7-00 

Large  bran  .         ,;•-. 

5-50 

4-75 

Offal  in  the  scouring  de-  1 
partment         .          .  j 

7-00 

7-00 

Dust  and  dirt  in  them  . 

4-50 

4-50 

CHAP,  viii]  tfLOUR   MILLING  563 

WHEAT  MILL,  VILLAGE  ALEXANDROVKA,  GOVERNMENT  OF 
EKATERINOSLAV 

The  samples  of  milling  are  of  the  1909  crop.  The  mill  treats  90  per 
cent,  of  Ulka  and  10  per  cent,  of  Garnovka. 

Semolina    ...  .          .          .          .          .  2 -5  per  cent. 

Flour,  brand  No.  000  .          .          .  2-5 

„  No.  00 15-0 

„  No.  0  .                    ...  10-0 

„  No.  1 10-0 

„  No.  2  ....  10-0 

„  No.  3 10-0 

„         „  No.  4 7-5         „ 

„  No.  5  .                                        .  6-25       „ 

Total  amount  of  flour          .         .         .     73 -75  per  cent. 

Fine  sharps          .         N.          .          .          .  1-25       „ 

Fine  bran  .          .  .  .     11-25      „ 

Large  bran          ....  7-50       „ 

The  above  tables  of  yields  and  flour  brands  through  their  variety 
and  inconstancy  greatly  impede  the  progress  of  the  Russian  exporters 
on  the  foreign  markets.  For  this  reason,  we  ought  most  decidedly  to 
adopt  uniform  brands.  There  is  no  doubt  that  a  reduced  number  of 
grades  and  the  definiteness  of  the  brand  will  simplify  the  milling  process, 
make  it  cheaper,  and  facilitate  the  competition  of  Russian  mills  on  foreign 
markets. 


CHAPTER   IX 

CONSTRUCTION   OF   MILL   BUILDINGS 

I 

CONDITIONS  DETERMINING  THE  CHARACTER  OF  BUILDINGS 

IN  milling  practice  there  are  two  processes  which  determine  the  character  of 
the  buildings  and  the  arrangement  of  the  machines  :  the  automatic  and  the 
intermittent.  For  this  reason,  before  proceeding  to  describe  the  construc- 
tions of  mill  buildings,  one  should  compare  these  two  methods  of  milling. 

In  automatic  milling,  as  the  name  itself  proves,  the  complex  milling 
process  is  performed  without  the  assistance  of  human  hands. 

In  the  sack  mill  all  the  intermediate  products,  beginning  with  break 
and  middlings  and  ending  with  dunst  and  flour,  are  sacked,  sorted,  and  fed 
by  hand  into  corresponding  machines,  where  they  are  subjected  to  further 
treatment.  Thus,  the  manual  operation  of  a  workman  forms  the  con- 
necting link  in  the  independent  work  of  the  separate  machines. 

"  Sack  mills  "  are  now  comparatively  seldom  met  with,  and  at  a  well- 
furnished  sack  mill  one  may  see  special  devices — generally  in  the  shape 
of  bins  with  so-called  caps — for  the  automatic  performance  of  the  different 
parts  of  the  milling  process,  such  as  the  breaking  process,  middlings 
grading,  or  reduction. 

If,  on  the  other  hand,  the  arrangement  of  the  mill  is  automatic,  the 
whole  process,  starting  at  the  moment  the  dirty  grain  goes  into  the 
storing  bin  and  ending  with  the  packing  of  flour  per  grade,  is  performed 
without  the  assistance  of  working  hands.  The  separate  products  by 
means  of  various  transporting  devices,  in  the  shape  of  bands,  elevators, 
worms  and  spouts  pass  through  all  the  stages  of  treatment,  i.e.  the  whole 
operation  is  performed  quite  automatically. 

In  this  manner,  the  continuity  of  the  milling  process  is  left  intact. 
If  a  certain  scheme  of  milling  is  accurately  followed,  both  the  auto- 
matic and  the  sack  mill,  provided  they  are  furnished  with  a  sufficient 
number  of  machines,  are 'able  to  give  equal  results  as  regards  the  quality 
of  the  milled  products.  But  here  arises  the  question,  Which  way  is  the 
best  to  obtain  these  results  ?  which  one  of  them  is  the  most  expedient, 
technically  speaking,  and  more  economical  as  regards  the  milling  costs  ? 

Among  the  mass  of  millers,  not  only  in  Russia  but  also  abroad,  there 

554 


CHAP,  ix]  FLOUR   MILLING  555 

are  many  partisans  of  the  full  sacking  or  semi-automatic  mill.  Therefore 
it  is  necessary  minutely  to  consider  the  question,  What  mill  should  one 
build — a  sacking  or  an  automatic  one  ?  First  of  all,  it  is  an  undoubted 
fact  that  every  machine  answers  its  purpose  only  when  its  work  is 
perfectly  definite  both  in  quantity  and  in  quality.  A  change  in  the 
quality  of  the  material  treated,  overloading,  and  frequent  half  empty  work- 
ing, while  the  material  is  being  changed, — all  this  has  a  detrimental 
influence  on  the  results  of  the  work  and  on  the  wear  of  the  machine.  All 
this  is  observed  in  the  work  of  the  sacking  mill,  in  which,  generally,  there 
is  no  sufficient  number  of  machines  and  apparatus  and  the  process  is  not 
strictly  established.  In  the  sacking  mill  one  and  the  same  machine  often 
serves  for  different  purposes.  In  the  medium  sacking  mill,  for  instance, 
there  are  often  adopted  the  so-called  "  turn,"  with  the  aid  of  which  one 
and  the  same  roller  mill  and  the  bolting  machine  coupled  to  it  treat  pro- 
ducts different  in  size  and  quality.  Under  such  conditions  neither  the 
number  of  corrugations  on  the  rolls  nor  the  number  of  the  sieves  in  the 
bolting  machine  can  be  common  for  different  products,  and  therefore  the 
quality  of  the  work  is  not  high. 

The  automatic  mill  operates  according  to  a  perfectly  definite  scheme 
of  milling.  A  sufficient  number  of  machines,  every  one  of  which  performs 
a  certain  work,  affords  the  possibility  of  establishing  a  definite  set  of 
dimensions  for  the  machines,  in  accordance  with  a  previously  evolved 
and  thought-out  milling  scheme.  The  whole  work  is  performed  evenly, 
and  the  corresponding  products,  mechanically  blending,  are  automatically 
sent  forward  for  further  treatment. 

In  an  automatic  mil^  having  a  definite  milling  scheme,  the  miller  is 
always  able  to  watch  the  general  run  of  the  process,  to  control  at  any 
given  moment  the  expedience  of  the  combinations  provided  for  by  the 
scheme.  On  the  other  hand,  there  is  always  provision  made  for  the 
construction  of  alternative  runs,  owing  to  which  the  scheme  becomes 
flexible,  and  this  allows  the  varying  demands  of  the  market  to  be  met, 
since  it  is  possible  to  alter  within  certain  limits  the  percentage  of  yields 
of  the  different  grades  of  flour. 

The  sacks  with  the  intermediate  products,  occupying  all  the  open 
spaces  in  the  sacking  mill,  and  the  shooting  of  these  products  by 
hand  into  the  bins,  result  in  the  mill  apartments  being  constantly  filled 
with  dust.  Even  with  the  most  careful  attendance  it  is  impossible  to 
avoid  the  escape  of  flour,  which  lowers  the  total  percentage  of  the  yield. 
That  loss  may  be  obviated  only  in  an  automatic  mill,  where  the  products 
travel  through  closed  spouts,  which,  coupled  with  a  suitable  system 


tfLOUR   MILLING 


[CHAP.  IX 


of  exhaust,  make  dustless  operation  possible  not  only  in  the  clean 
half  of  the  mill — the  milling  department — but  also  in  the  grain-cleaning 
division.  By  adopting  filters  one  can  make  all  the  apartments  of  an 
automatic  mill  dustless,  for,  not  only  machines  furnished  with  fans 
may  be  included  in  the  general  exhaust  system,  but  such  machines  and 
apparatus  as  the  trieurs,  automatic  scales,  and  elevators  as  well. 

When  selecting  the  type  of  mill,  a  circumstance  of  no  less  importance 
than  the  technical  outfit  is  the  economic  side  of  the  question,  which 
touches  the  millers'  most  tender  point — the  cost  of  working  the  milling. 

The  most  material  element  in  the  milling  expenses  is  the  cost  of  mill 
hands.  If  a  large  mill  is  taken,  a  parallel  comparison  of  an  automatic 
and  a  sacking  mill  shows  a  sharp  difference.  For  instance,  in  a  mill  of 
the  sacking  type,  with  a  12,000  bushels  of  wheat  capacity  per  day,  the 
expenses  in  workmen  during  one  shift  amount  to  the  round  figure  of 
seventy  hands,  while  in  an  automatic  mill  of  the  same  capacity  the 
number  of  workmen  is  reduced  almost  fourfold  down  to  eighteen  men. 
That  relation  drops  also  with  the  lowering  capacity,  and,  for  instance, 
for  a  medium  mill  of  1750  bushels  automatic  in  arrangement  the  number 
of  hands  does  not  exceed  five  or  six.  against  the  ten  or  twelve  of  the  sack- 
ing system. 

The  numbers  of  hands  given  include  only  the  persons  taking  part  in 
the  process  of  production,  for  instance,  roller  men,  purifier  men,  &c., 
whereas  the  workmen  occupied  in  supplying,  loading  of  the  wheat,  the 
packing  of  the  flour  are  not  reckoned,  as  their  number  depends  on  local 
conditions — the  situation  of  the  mill,  the  mode  of  transport,  &c. 

The  following  table  gives  parallel  data  pertaining  to  the  number  of 
hands  employed  during  one  shift  at  a  sacking  and  an  automatic  mill. 

TABLE  LXI 


Number  of  Hands. 

Capacity  of  Mill  per  Day 
in  Bushels. 

Sacking  Mill. 

Automatic  Mill. 

Milling  Dept. 

Cleaning  Dept. 

Total. 

Milling  Dept.  j  Cleaning  Dept. 

Total. 

12,000      ,.     .    , 

66 

4 

70 

14 

4 

18 

8000    .     .     .  ;  ; 

36 

3 

39 

9 

3 

12 

5500  to  6000      . 

24 

3 

27 

7 

3 

10 

4000     .... 

20 

2 

22 

5 

2 

7 

2700  to  3300      . 

16 

2 

18 

5 

2 

7 

1700  to  2000      . 

10 

2 

12 

4 

2 

6 

1000     ...     .. 

6 

1 

7 

3 

1 

4 

CHAP,  ix]  FLOUR   MILLING  557 

As  may  be  seen  in  the  table,  in  the  grain- cleaning  department  of 
the  automatic  mills  there  is  employed  the  same  number  of  hands  as  in 
the  sacking  mills,  because  the  cleaning  of  grain  at  a  sacking  mill  is  gene- 
rally performed  automaticaUy.  But  in  the  grinding  department  of  the 
mill,  the  number  of  hands  in  changing  from  the  sacking  to  the  automatic 
mill  makes  a  sharp  bound,  as  we  see  in  Fig.  521,  which  presents  more 
strikingly  the  data  of  the  appended  table. 

This  diagram  clearly  shows  that  with  the  diminution  of  the  capacity 
the  difference  drops,  and  attains  an  insignificant  quantity  in 
small  mills. 

To  the  milling  expenses,  which  are  absent  in  the  automatic  arrange- 


Number  of  hands  in  the  grain- 
cleaning  department. 

•I  Number    of    hands    in    an 
automatic  mill. 

•s°°  v  w~m  arm  ^»mber  °f  ***** «« » 

sacking  mill. 
FIG.  521. 

ment,  must  be  added  also  the  outlay  in  sacks  for  the  intermediate 
products. 

Besides  the  cost  of  working,  one  should  reckon  the  cost  of  equipping 
the  mill,  which  determines  the  capital  charges. 

The  automatic  mill  requires  a  greater  number  of  machines,  the  presence 
of  which  would  exclude  the  necessity  of  a  "  return  "  to  the  machines  which 
have  already  fulfilled  one  purpose.  Consequently,  the  automatic 
mill  requires  far  more  machinery  in  the  grinding  section  than  the 
sacking  one. 

For  example,  we  shall  take  a  mill  with  650  bushels  of  wheat  capacity 
per  day.  In  mills  fitted  out  for  sacking,  very  frequently  owing  to  the 
use  of  "  returns  "  the  number  of  roller  mills  is  limited  to  four,  whereas  an 
automatic  mill  of  the  same  capacity  to  work  regularly  needs  seven  or 
eight  roller  mills.  Parallel  to  the  number  of  those  mills  the  number  of 
bolting  machines  and  transport  devices  augments,  which  increases  the 
posts  of  the  pla^nt.  As  the  capacity  increases,  however,  these  ex* 


558  FLOUR   MILLING  [CHAP,  ix 

penses  decrease.  For  a  mill  with  2000  bushels  of  wheat  capacity  per 
day,  of  the  sacking  type,  eight  is  a  sufficient  number  of  roller  mills, 
whereas  an  automatic  mill  needs  but  eleven  mills. 

In  spite  of  the  comparatively  great  difference  in  cost  of  fitting  out  an 
automatic  and  a  sacking  mill  at  the  present  moment,  the  erection  of  an 
automatic  mill  may  be  regarded  as  profitable  as  soon  as  its  capacity 
amounts  to  1000  or  1300  bushels. 

Those  against  the  automatic  mill  maintain,  though  without  any  founda- 
tion, that  the  flour  produced  by  an  automatic  mill  does  not  possess 
uniform  qualities.  Under  the  influence  of  that  false  opinion  there  sprang 
into  existence  a  type  of  mills  which  find  their  place  on  the  line  between  the 
automatic  and  the  sacking  mills.  The  peculiarity  of  these  so-called 
semi-automatic  mills  consists  in  the  fact  that  the  whole  process  is  per- 
formed automatically,  but  the  flour  is  collected  in  sacks  at  the  point 
of  discharge  out  of  separate  bolting  machines  and  then  graded  by  hand 
and  mixed  in  the  blender  to  obtain  the  brands  established  on  the  market. 
But  this  is  a  palliative,  which  does  not  abolish  the  causes  of  non-uni- 
formity of  the  flour. 

In  the  meantime,  not  noticing  it  themselves,  these  opponents  of  the 
automatic  system  turn  the  above-mentioned  argument,  which  has  some 
real  meaning  in  it,  against  themselves:  namely,  the  sacking  mill  does 
not  guarantee  the  uniformity  of  the  consistence  of  flour,  the  whole 
control  being  based  on  the  superficial  visual  sensations.  But  at  the  time 
of  the  night  shift  that  becomes  almost  impossible  even  to  an  experi- 
enced miller. 

To  solve  the  question  of  the  homogeneity  of  flour  in  the  automatic 
mill,  one  must  pay  due  attention  to  the  methods  of  blending  the  grain, 
a  no  less  important  question  than  the  cleaning  of  it.  For  the  regularity 
and  consistency  of  the  final  results,  the  uniformity  of  the  intermediate 
products,  middlings  and  dunst,  is  equally  necessary.  The  ideal 
solution  of  the  question  is  to  erect  elevators  by  the  mills  in  which 
the  grain  is  stored  in  silos,  sorted,  and  the  mill  supplied  with  a 
mixture  according  to  a  certain  recipe.  Then  the  intermediate 
products  too,  being  the  result  of  a  definite  milling  scheme,  will  be 
homogeneous. 

Thus,  for  a  mill  of  even  a  medium  capacity  the  automatic  type, 
unrestricted  as  regards  the  number  and  size  of  machines,  is 
undoubtedly  the  most  rational  type,  both  economically  and  theo- 
retically. 


CHAP,  ix]  FLOUR   MILLING  559 

II 

CONSTRUCTION  OF  MILL  BUILDINGS 

With  the  introduction  of  the  automatic  process  in  flour  mills,  material 
alterations  in  the  construction  of  the  mill  buildings  became  necessary. 
Up  to  that  time  low  mill  buildings  answered  their  purpose  perfectly. 

At  the  old  (village)  mills  of  plain  grinding  with  water-wheels  the  plant 
consisted  mainly  of  one  stone  mill  and  one  bolting  reel  per  wheel. 
For  small  country  mills  an  insignificant  building  area  by  the  water  for 
the  machinery  was  sufficient,  while  the  remaining  part  of  the  building 
was  free  for  other  purposes  and  served  as  lodging  to  the  miller. 

The  idyllic  situation  of  the  mill  by  the  water,  the  rumbling  torrent, 
and  the  roar  of  the  mill,  all  wakened  the  creative  powers  in  the  poets, 
who  sang  praises  to  the  outward  picture  of  manual  industry. 

With  the  invention  of  the  turbine  at  the  large  sources  of  water  energy, 
plants  consisting  of  several  separate  wheels  were  substituted  by  the 
turbine,  owing  to  which  the  inner  arrangement  became  more  independent 
of  the  outer. 

When  steam  power  commenced  its  victorious  march  from  England 
over  all  the  civilised  countries,  and  effected  in  all  branches  of  industry 
the  well-known  great  changes,  flour  milling  could  not  remain  behind 
in  the  general  progressive  motion. 

The  invention  of  the  roller  mill,  and  the  adoption  of  steam-engines 
and  other  heat  motors  together  with  it,  imparted  a  totally  different  aspect 
to  the  milling  industry.  The  construction  of  mills,  which  up  to  that 
time  was  mostly  in  the  hands  of  artisans,  developed  into  a  large  industry, 
and  by  the  efforts  of  mill-building  firms,  during  the  course  of  the  last 
forty  years  there  was  evolved  a  certain  form  of  arrangement  of  the  mill 
apartments,  which  may  be  regarded  as  fairly  standardized. 

A  Simple  Mitt  Building. — Let  us  first  examine  the  type  of  building 
of  a  simple  mill  for  the  peasant  single  grinding.  Fig.  522  illustrates  in  a 
longitudinal  section  and  plan  a  mill  with  one  stone  mill  (on  ball  bearings), 
a  combined  grain-cleaning  machine,  a  cyclone  for  dust  collecting,  and 
Soder's  sifter. 

The  single  floor  building  has  a  hursting  on  which  the  sifter  is  set. 
The  stone  mill  is  planted  on  a  foundation  on  a  level  with  the 
hursting. 

On  the  overhead  flooring,  to  which  there  runs  a  ladder,  a  cyclone  and 
a  grain-cleaning  machine  are  stationed :  under  the  flooring  the  main 


560 


FLOUR   MILLING 


[CHAP,  ix 


drive  is  placed,  from  which  the  motion  is  communicated  to  the  elevator, 
the  grain-cleaning  machine,  and  the  sifter.     For  the  motor  (in  our  case  a 


a— Grain  bin. 
fc— Grain  elevator. 
c — Scourer. 
d— Ball  mill. 


e — Flour  elevator. 
k— Plansifter. 
I— Hoisting  device. 
t — Dust  collector. 


FIG.  522. 


naphtha-engine,  but  it  may  be  a  steam-engine  or  a  turbine)  a  special 
apartment,  separated  from  the  mill  by  a  wall,  is  arranged.  The  building 
may  be  of  stone,  which  is  better  as  regards  security  against  fire. 


CHAP.    IX J 


FLOUR    MILLING 


561 


III 
BUILDINGS  or  COMPLICATED  GRINDING  MILLS 

In  modern  wheat  or  rye  mills  with  automatic  handling  of  the  prQ- 
ducts  we  generally  find  four  or  five  floors.  The  first  (basement)  floor  is 
left  for  the  main  shafts,  the  second  for  the  roller  mills,  the  third  is 
necessary  for  the  purpose  of  communicating  a  sufficient  incline  to  the 
spouts,  the  fourth  for  purifiers,  and  finally,  the  fifth  for  bolting  machines. 
In  rye  mills  there  is  no  floor  for  purifiers. 

The  roller  mills  and  stone  mills,  as  well  as  the  purifiers  and  bolting 


FIG.  523. 


FIG.  524. 


machines,  are  placed  in  straight  rows  along  the  building.  For  each  roller 
passage  there  is  a  separate  elevator,  which  runs  through  all  the  floors  ; 
besides  that  elevators  are  needed  for  other  machines  from  which  the 
product  cannot  be  allowed  to  flow  of  its  own  accord.  It  is  these  transport 
devices  which  have  a  very  considerable  influence  on  the  arrangement  of 
the  mill  building  and  especially  on  the  shape  of  its  roofing. 

Let  us  now  inspect  the  most  typical  mill  buildings. 

In  Fig.  523  may  be  seen  the  transverse  section  of  a  mill  with  two 
rows  of  roller  mills  and  two  rows  of  plansifters.  The  elevators  are  set 


562 


FLOUR   MILLING 


[CHAP,  ix 


in  the  middle.  Such  an  arrangement  may  be  particularly  recommended  for 
rye  mills,  by  reason  of  its  cheapness,  because  from  both  the  rows  of  mills 
the  product  by  its  weight,  without  the  aid  of  worms,  runs  to  the  elevators 
as  well  as  into  the  bolting  machines.  The  roof  of  such  a  building  should 
have  a  high  ridge,  so  as  not  to  increase  the  height  of  the  floor  holding  the 
sifters  for  the  sake  of  the  elevators.  The  sole  defect  of  such  an  arrange- 
ment of  the  outfit  is  that  the  elevators  block  up  so  much  space  in  the 
centre  of  the  mill  building.  The  free  passage  between  the  machines  and 
the  inspection  of  their  operation  are  impeded.  For  this  reason,  though 
such  an  arrangement  is  sometimes  practised  in  wheat  mills,  it  cannot  be 
recommended,  as  the  number  of  elevators  here  is  still  greater.  Figs.  525 
and  526  show  us  the  cross  sections  on  which  out  of  the  above  considera- 
tions the  elevators  are  arranged,  not  in  the  middle,  but  by  the  wall.  With 

such  an  arrangement  all 
the  sections  remain  free 
in  the  middle  and  easily 
accessible  to  inspection. 
The  elevators  are  set  along 
the  wall  so  as  not  to  stand 
opposite  to  the  windows. 
The  walls  of  the  top  floor 
have  to  be  sufficiently  high 
for  the  elevators  (here 
they  are  5  metres  high,  while  in  the  first  case  the  height  is  only  2  metres), 
so  that  the  roof  is  flat  in  shape.  Such  an  arrangement  of  the  building  in 
practice  appears  to  be  the  most  efficient'  both  for  large  and  for  small 
mills,  and  is  therefore  the  one  most  frequently  adopted. 

On  Fig.  524  the  mill  building  is  divided  by  a  longitudinal  stone  wall 
into  two  parts,  of  which  one  serves  as  the  mill  proper,  and  the  other  as  a 
warehouse  furnished  with  flour-blenders.  If  the  mill  has  to  be  enlarged 
the  warehouse  may  be  used  for  setting  the  machinery  in.  There  is  no 
floor  to  allow  of  inclining  the  spouts  ;  instead  of  the  spouts  there  are 
worms  set  over  the  mills.  The  double  slope  roof  leaves  sufficient  space 
for  the  high  elevators  and  detachers,  which  are  situated  over  the  sifters 
of  the  reduction  rolls.  With  such  a  construction  of  the  building  one  has 
to  make  much  use  of  the  worms,  but  by  disposing  the  machines  rationally 
along  the  building  their  number  may  be  considerably  reduced. 

Fig.  527  presents  a  cross  section  of  a  large  modern  mill.  The  height 
of  the  building  here  is  quite  considerable.  The  ground  floor  is  so  high 
that  the  product  of  itself  runs  to  the  elevators  from  both  rows  of  mills. 


CHAP.    IX] 


FLOUR   MILLING 


563 


The  floors  for  the  spouts  and  the  cleaning  department  are  also  sufficiently 
high,  so  as  to  have  the  product  travel  automatically  if  possible  everywhere, 
requiring  the  least  quantity  of  power  for  transport.  The  ceilings  of 
the  building  are  of  a  peculiar  construction  (A,  Fig.  529 — this  construc- 


FIG.  526. 


FIG.  527. 


tion  comes  from  England).  Here  steel  joists  are  laid  across  the 
building  at  about  2J  metres  distance  from  each  other.  On  these  joists 
there  lie  narrow  beams,  and  the  whole  is  covered  with  a  solid  layer  of 
square  beams  some  10  cm.  thick,  on  which  there  is  another  layer  2J  cm. 
thick.  Such  ceilings  are  comparatively  expensive,  but  their  advantage 
lies  in  the  fact  that  the  ceiling  beams  are  nowhere  in  the  way.  The 


564  FLOUR    MILLING  [CHAP,  ix 

suspended  bearings  of  the  main  shafts  are  attached  directly  to  the  iron 
joists. 

Altogether  the  construction  of  the  ceilings  in  mill  buildings  has 
assumed  a  very  peculiar  shape,  which  depends  on  the  disposition  of  the 
machines,  and  the  practical  utilisation  of  space  in  the  mills. 

On  Figs.  525  and  528  (transverse  and  longitudinal  sections)  we  see  a 
framing  of  joists  often  used  in  other  buildings  too.  The  cross  pieces  a 
^,re  timber  beams  with  supports  b  at  the  fulcrums  of  the  columns  ; 
these  supports  are  designed  to  shorten  the  length  of  the  unsupported 
part  c,  in  consequence  of  which  the  beam  has  a  more  rigid  span.  The 
supports  b  are  strengthened  with  rafter  beams  d  or  attached  to  the  beam  a 
by  means  of  bolts  e,  which  produces  the  same  result  and  is  often  considered 
to  be  more  convenient.  The  joists  /  are  disposed  at  a  distance  of  0-8  or 
1  metre  from  each  other.  Care  should  be  taken  that  these  joists  are 

set  exactly  vertically  over  each  other  in  all 
the  floors.  The  columns  supporting  the 
ceilings  are  either  single  like  g,  or  double 
like  h  (Fig.  525).  When  using  timber  joists 
and  cross  pieces  the  distance  between  the 
supporting  columns  should  not  be  over  4 
or  4J  metres  in  longitudinal  and  in  trans- 
versal direction.  The  breadth  of  the  build  - 
*  ing  being  8  or  12  metres,  there  are  con- 

FIG.  528. 

sequently  two  or  three  rows  of  columns. 

For  mills  with  a  capacity  of  240  sacks  per  da^  such  an  arrangement 
is  advantageous,  as  its  erection  costs  comparatively  little.  But  for  mills 
of  larger  dimensions  this  arrangement  is  disadvantageous  as  regards  the 
most  economic  use  of  the  area  of  the  buildings.  As  we  see  in  Fig.  525, 
the  rows  of  columns  allow  of  freely  setting  in  the  4-15  metre  spans  only 
three  rows  of  mills  and  sifters,  whereas  with  the  Fig.  526  construction 
of  ceiling  there  is  space  for  four  such  rows.  In  Fig.  526  there  is  a  row 
of  columns  only  in  the  middle,  the  distance  between  the  columns  and  the 
walls  being  6J  metres.  For  such  a  span  the  timber  cross  beams  of  the 
limit  size  would  be  too  weak,  and  therefore  the  cross  pieces  here  are 
I-beams,  while  the  timber  ceiling  joists  run  down  the  length  of  the  build- 
ing with  a  distance  of  4  metres  between  the  fulcrums.  The  roller  mills 
and  sifters  of  the  second  row  are  connected  with  eLvators  by  means  of 
transverse  worms.  The  advantage  of  the  sifters  over  reels  and  centri- 
fugals as  regards  economy  of  the  area  occupied  is  clearly  seen  here,  for, 
with  centrifugals,  jt  is  quite  impossible  to  instal  in  the  same  space  a 


A 


ix]  FLOtJR   MILLING  565 

machine  doing  the  same  work  or  to  keep  at  the  same  time  the  dressing 
surface  as  accessible  to  inspection  as  when  furnished  with  sifters. 

The  danger  of  fire  that  threatens  the  mill,  led  to  the  necessity  for  con- 
structing fireproof  buildings.     The  machines  and  apparatus  as  well  as 
the  transport  devices  of  the  fireproof  mills  have  no  wood  parts  whatever. 
Not  only  the  walls,  ceilings,  and  coverings  of  the 
building  have  to  be  of  fireproof    materials,  but     A  lilTL. l^ZJC! 
the  doors  and  windows  as  well.  "TT~ 

The  buildings  of  a  fire-resisting  mill,  i.e.  pro- 
perly speaking  the  walls,  are  erected  of  ordinary 
brick.  Only  comparatively  recently  in  America  at- 
tempts at  complete  ferro-concrete  buildings  or  steel 
constructions  with  a  brick  shell  have  been  made .  As 
regards  ceilings,  there  are  two  types :  solid  ferro- 
concrete (B,  Fig.  529)  and  with  concrete  arches 

(C,  Fig.  529)  between  the  longitudinal  iron  beams.  *  The  last  construction 
is  the  heavier  of  the  two,  and  is  therefore  inferior  to  the  first. 

Such  in  a  general  outline  are  the   constructions  of  mill  buildings 
answering  the  requirements  of  modern  technics. 


IV 

CONSTRUCTION  OF  AMERICAN  MILLS 

The  originality  of  American  technics  shows  itself  also  in  the  construc- 
tion of  mill  buildings. 

A  more  or  less  normal  type  of  an  American  mill  building,  approaching 
the  European  construction,  is  given  in  Figs.  530  and  531,  which  illus- 
trate the  cross  section  of  the  grain-cleaning  department  and  a  longitudinal 
section  through  the  grain-cleaning  and  milling  departments.  The 
principal  difference  from  the  European  constructions  of  buildings  lies  in 
the  fact  that  the  ground  floor  is  considerably  higher.  That  is  necessi- 
tated by  the  type  of  roller  mills  used,  which  need  overhead  shafting  hung 
from  the  ceiling  and  special  tension  pulleys  for  the  flexible  gearing. 

On  the  ground  floor  the  flour  is  packed,  on  the  first  the  roller 
mills  are  disposed,  on  the  second  the  suspended  filters,  on  the  third  the 
purifiers,  on  the  fourth  the  centrifugals  and  vertical  scouring  bran  dusters 
for  freeing  the  bran  of  the  flour  remaining  in  it,  on  the  fifth  sifters. 

The  grain-cleaning  department  is  supplied  with  hard  and  soft  wheat 
by  the  band  conveyors  SBC  and  HBC.  That  wheat  is  hauled  up  by  the 
elevator  and  of  itself  flows  into  the  worm  C  10.  This  worm  distributes 


.  ix] 


FLOUR   MILLING 


507 


the  grain  to  the  bins  MR.  In  proportion  as  it  is  needed,  it  is  let  out  of 
the  bins  into  the  worm  C  1  and  passes  to  the  automatic  scale  AS,  whence 
it  pours  into  the  elevator  7,  and  is  then  carried  up  to  be  cleaned. 


FIG.  532. 

In  cases  where  the  scale  of  output  goes  far  beyond  the  limits  of 
the  ordinary  dimensions,  the  American  mill  buildings  are  amazing  in 
their  size  and  originality.  Figs.  532,  533.  and  534  show  us  the 


56S 


FLOUR   MILLING 


[CHAP. 


sections  of  an  American  mill  belonging  to  Hecker  Jones  Jewell  in  New 
York,  started  in  1908,  and  working  mostly  for  export. 

The  capacity  of  the  mill  is  8000  sacks  of  wheat  grist  per  day.     To 


FIG.  533. 


give  an  idea  how  big  that  mill  is,  it  is  sufficient  to  say  that  there 
are  115  four-roller  mills  250x900  mm.  in  size  in  it,  and  it  is  brought 
into  operation  by  two  compound  steam-engines  of  1800  and  1000  indi- 
cated horse-power. 


CHAP.   IX 


FLOUR   MILLING 


569 


The  concrete  foundation  of  the  mill  is  laid  on  concrete  piles.  The 
underground  floor  serves  for  the  boots  of  the  elevators.  The  first,  second, 
and  third  floors  do  duty  as  temporary  stores  for  barrels  of  flour,  the  third 
and  partly  the  fourth  floors  being  for  packing.  The  transportation  of 


FIG.  534. 

sacks  and  barrels  to  the  second  and  first  floors  is  performed  by 
conveyors.  The  fourth  floor  contains  the  driving  machinery,  the  fifth 
is  for  roller  mills.,  the  sixth  for  the  transmission  drive  and  for  the 
corresponding  deflection  of  the  spouts,  the  seventh  and  eighth 
for  purifiers  and  centrifugals,  the  ninth  for  sifters,  and  the  tenth 
is  the  garret  for  star  filters.  The  milling  department  (Fig.  533) 


570  FLOUR   MILLING  [CHAP,  ix 

is  divided  by  a  party-wall  into  two  separate  mills  (4800  and  3200 
sacks). 

The  grain-cleaning  department  (Fig.  532)  has  a  washing  plant  and 
roller  mills  on  the  tenth  floor  for  the  reduction  of  the  broken  grain  and 
screenings  to  feed.  On  the  fifth  floor  there  are  set  the  feed  and 
part  of  the  bran  packers  for  the  stock  which  is  transmitted  from  the 
milling  department. 

The  longitudinal  section  of  the  mill  is  shown  on  Fig.  534.  The  mill 
is  built  according  to  the  fireproof  type. 

Worthy  of  notice  is  the  truly  American  rapidity  with  which  that  mill 
was  erected.  The  construction  of  the  mill  building,  the  elevator  to  it 
(for  500,000  bushels  of  grain),  and  the  full  equipment  were  ended  in  eight 
months.  The  building  was  started  on  the  1st  of  May,  1907,  and  on 
2nd  January,  1908,  the  milling  operation  was  in  full  swing. 


V 
PLANS  or  MILLS 

The  longitudinal  and  transversal  sections  of  the  mills  we  have  examined 
illustrate  to  a  certain  extent  their  general  plan.  But  it  is  necessary  to 
give  a  general  outline  of  the  distribution  of  machinery  and  also  of  the 
position  of  the  prime  motor. 

In  Fig.  535  may  be  seen  the  plan  of  the  ground  floor,  where  A  is  the 
grain-cleaning  department,  B  the  milling  department,  C  the  engine  room, 
and  D  the  boiler  plant.  This  plan  shows  that  the  necessity  of  securing 
the%mill  against  fire  compels  the  constructors  to  isolate  the  engine  room 
from  the  mill  proper.  The  position  of  the  engine  room  pointed  out  is 
convenient  in  so  far  that  it  occupies  a  small  area  together  with  the  mill 
building.  But  its  inconvenience  lies  in  the  fact  that  a  series  of  roller 
mills  by  the  windows  looking  on  to  the  wall  of  the  boiler  room  D,  is  in 
the  dark.  It  is  better  to  arrange  the  boiler  room  down  the  longitudinal 
axis  of  the  engine  room,  if  space  permits. 

Further,  it  is  necessary  to  isolate  by  a  staircase  the  grain-cleaning 
department  from  the  milling,  to  prevent  fires,  which  generally  break 
out  in  the  former,  from  penetrating  into  the  latter.  In  this  plan,  as  well 
as  in  others,  we  see  that  from  the  landings  of  the  staircase  the  doors  open 
into  the  milling  and  grain-cleaning  departments.  That  is  the  ordinary 
planning  in  Russia  and  in  Western  Europe.  It  is  inexpedient,  however, 
in  case  of  fire,  because  the  flames  can  easily  leap  from  door  to  door 


CHAP,  ix ] 


FLOUR   MILLING 


571 


across  the  landing  on  the  staircase.  It  is  better  to  have  balconies  made 
opposite  to  the  landings,  which  afford  communication  between  the  grain- 
cleaning  department  and  these  landings,  and  to  have  the  wall  of  that  de- 
partment quite  blind,  leaving  one  door  from  the  landing  to  the  balcony 
and  one  into  the  milling  department. 

To  return  to  the  engine-house,  it  should  be  noted  that  the  area  it 
occupies  is  considerably  reduced  when  an  internal  combustion  engine  is 
employed,  and  there  is  np  need  for  space  for  the  boilers. 


•IfHMMHSG^^ 


Co    flu*  it  iHO^HMHtfHHI^iMf 


V 


IHHi<^^!^ 

'          i    |    l         ,J  I  I 1  ..LL.- J±=r 


FIG.  535. 


Fig.  536  illustrates  the  plan  of  the  first  and  second  floors  in  a  wheat 
and  a  rye  mill  with  a  silo  :  A  is  the  milling  department  of  the  wheat 
mill,  B  the  stairway,  C  the  common  wheat  and  rye  grain-cleaning 
department,  D  the  milling  department  of  the  rye  mill,  and  E  an  elevator 
with  rectangular  silos. 

The  plan  of  the  second  and  the  following  floors  shows  that  part  of  the 
stairway  is  occupied  by  bins  for  tempering  the  grain.  The  flour  bins 
are  marked  a.  In  the  same  plan  of  the  second  floor  there  are  shown 
two  types  of  disposition  of  the  roller  mills,  in  a  chess-board  order  and 
along  the  general  transversal  line. 

In  the  arrangement  of  the  roller  mills,  as  well  as  of  other  machinery, 


572 


FLOUR   MILLING 


CHAP.    IX 


FIG.  536. 


CHAP.    IX  | 


FLOUR   MILLING 


573 


-4-«f-         --£ 


537. 


574 


FLOUR    MILLING 


[CHAP,  ix 

one  should  be  guided  by  their  accessibility  from  all  sides,  which  guaran- 
tees a  free  inspection  and  allows  repairs  to  be  done  in  situ. 

With  the  third  and  fourth  floors  (Fig.  537)  the  rye  mill  and  the  grain 

Sixth  Floor. 


FIG.  538. 

elevator  end.  On  the  fourth  floor  of  a  wheat  mill  are  set  the  purifiers, 
and  on  the  same  of  a  rye  mill  the  sifters ;  the  fifth  and  sixth  garret  - 
floors  of  a  wheat  mill  contain  sifters  (Fig.  538). 

The  above  plans  represent  the  scheme  for  an  800  sacks  per  day  mill, 
drawn  up  by  the  firm  of  Dobrovy  &  Nabholtz  for  a  South  Russian  mill. 


CHAPTER   X 

THE  COST. OF  ERECTING  AND  OF  WORKING  MILLS 


THE  MILL  BUILDING  AND  EQUIPMENT 

RUSSIAN  general  practice,  and  consequently  literature  also,  give  no 
materials  whatever  from  which  the  average  data  concerning  the  area 
required  for  a  mill  may  be  deduced,  not  to  mention  its  costs  per  certain 
capacity.  This  is  explained  by  the  fact  that  Russian  milling  conditions 
as  a  whole  are  so  different,  that  the  building  firms  very  often  ignore  the 
types  of  mills  and  milling  standards  established  in  Western  Europe. 

It  is  equally  impossible  to  give  the  average  costs  of  a  mill  equipment 
according  to  its  capacity,  as  the  prices  of  the  machinery  and  of  erection 
also  fluctuate  within  wide  limits. 

In  Germany,  where,  as  we  have  seen,  a  definite  type  of  mill  has  been 
evolved,  and  the  prices  for  machinery  and  labour  are  almost  without 
variation,  the  average  costs  are  deducible. 

We  append  here  Kettenbach's  table,  which  gives  us  the  capacity  per 
day,  the  total  area  of  a  wheat  and  a  rye  mill,  including  the  mill  building, 
and  the  full  cost  of  the  building  machinery  and  equipment  in  German 
marks. 

TABLE  LXII 


Total  Area  of  the 

Cost  of  Erection  in  Marks. 

Capacity  per  24  hours 
in  Kilograms. 

Mill  in  Square 
Metres. 

Wheat  Mill. 

Rye  Mill. 

20,000 

700 

200,000 

150,000 

30,000 

900 

300,000 

240,000 

40,000 

1250 

400,000 

300,000 

50,000 

1500 

500,000 

380,000 

60,000 

1800 

600,000 

450,000 

80,000 

2100 

800,000 

600,000 

100,000 

2500 

1,000,000 

750,000 

120,000 

3000 

1,200,000 

850,000 

150,000 

3500 

1,500,000 

1,000,000 

200,000 

4000 

2,000,000 

1,500,000 

575 


576  FLOUR    MILLING  [CHAP,  x 

The  data  of  that  table  are  taken  from  practice,  but  we  'presume 
that  the  quantities  here  are  rounded  off  with  great  approximation, 
since  according  to  the  table  the  costs  of  one  klg.  of  capacity  for 
small  as  well  as  for  large  wheat  mills  is  one  and  the  same,  10 
marks,  whereas  that  cost  ought  to  drop  with  an  increase  in  the  capacity 
of  the  mill. 

The  truth  of  this  statement  may  be  proved  by  Kettenbach's  other 
tables,  where  the  costs  of  a  full  equipment  of  an  automatic  mill  yield- 
ing one  sack  per  24  hours  are  given. 


TABLE   LXIII 
COST  OF  EQUIPPING  A  WHEAT  MILL 


Capacity  per  Day  (24  Hours). 

Cost  per  1  Sack  per  Day. 

200 
400 
800 
1,200 

to     400  sacks  =  20,000  to    40,000  klg. 
„      800     „      =  40,000  „      80,000     „ 
„  1,200     „     ==    80,000  „    120,000     „ 
„  2,000     „      =  120,000  „   200,000     „ 

350  marks 
320      „ 
300      ,. 

280      ,. 

TABLE  LXIV 

COST  OF  EQUIPPING  A  RYE  MILL 


Capacity  per  Day  (24  Hours). 

Cost  per  1  Sack  per  Day. 

—   to 

100 

sacks  = 



to    10,000 

klg. 

450 

marks 

200    „ 

400 

„     = 

20,000 

„    40,000 

33 

260 

j, 

400   „ 

800 

33 

40,000 

„     80,000 

33 

240 

3  3 

1,000   „ 

2,000 

3>             

100,000 

„  200,000 

33 

220 

3  3 

This  is  more  clearly  shown  in  the  diagram,  Fig.  539.  On  the  horizontal 
line  the  capacity  of  the  mill  per  day  (from  10,000  to  200,000  klg.)  is 
marked,  on  the  left-hand  side  vertical  (ordinate)  the  total  cost  of  equip- 
ment in  1000  marks,  on  the  right-hand  vertical  the  cost  per  one  sack 
per  twenty-four  hours  in  marks.  The  uninterrupted  line  (—  — ) 
running  upwards  denotes  the  diagram  of  cost  of  equipping  a  wheat 
mill ;  the  semi-dotted  line  ( —  .  -  -  ,  -  - ,  — )  the  cost  of  equipping  a 
rye  mill. 


CHAP.    X] 


FLOUR   MILLING 


577 


The  diagram  drawn  in  the  broken  line  ( )  gives  the  cost  of  equip- 
ment per  sack  per  24  hours  for  a  wheat  mill,  and  the  dotted  line  ( ) 


#00 

sooo 
J2 

1    **° 

fll 

1    foo 

I  *°° 

o      500 

1     loo 

JOO 
0 

poo 

foo 
4-00 
300 
2,00 
SOO 

^ 

^ 

x 

^ 

Xl 

? 

,> 

—  ^ 

-  -  —  , 

-  -  —  , 

-  . 

^r 

x- 

^ 

^' 

„.  -^ 

—  - 

.__ 

^ 

-—  . 

*•< 

—  - 

^ 

•^ 

^^ 

^--g 

1  — 

— 

— 

^ 

<* 

> 

"-" 

K 

-H 

-- 

••• 

x 

^.x 

*•" 

^ 

^" 

X 

^ 

SOOOO                     SOOOO                            SOOOOO                         SS0  O00                          lOOOOO^fn 

FIG.  539. — Capacity  per  24  hours. 

for  a  rye  mill.     It  is  clearly  seen  here  that  with  the  rise  in  the  capacity 
of  the  mill  the  cost  of  equipment  per  unit  of  capacity  drops. 


II 

CALCULATION  OF  WORKING  EXPENSES 

Motive  Power. — Before  defining  the  cost  of  the  motive  power  which 
constitutes  the  main  expenditure  in  working  the  mill,  the  data  of   the 


sso 

500 


$00 


ZOO 


M 
8 

II 

a  W 

I* 


FIG.  540.— Capacity  of  MiD. 

power  consumption  in  accordance  with  the  mill  capacity  should  be  noted 
briefly. 

In  Fig.  540  we  have  a  diagram  of   power  consumption  in  effective 

horse-power    for   automatic    wheat    mills    of    from    10,000   to   200,000 

2  o 


578  FLOUR    MILLING 

klg.   capacity.     The  uninterrupted  line  (— 


[CHAP,  x 


)  represents  the  out- 
put of  the  motor,  the  horse-power  of  which  is  shown  on  the  left- 
hand  side  ordinate  up  to  550  H.P.  ;  the  semi-dotted  line  indicates  the 
power  consumption  for  100  klg.  per  day.  The  last  diagram  shows  that 
with  the  increase  in  the  capacity  of  the  mill  the  power  consumption  to  a 


§5 


Output  of  the  Motor  for  the  whole  Mill. 

V  N  9*  t  ^  o\ 

*  *  1  §  §  §  §  * 

f  -1 

& 

2 

^ 

I/ 

^ 

v 

^ 

^ 

x 

/- 

/ 

—  •  - 

— 

/ 

^ 

.». 

-.- 

/ 

/* 

^^ 

/ 

/ 

/ 

X 

/ 

^X 

JOOOO                         SOOOO                                  SOOOOO                              SSCOOO                                ZOO  000  1 

FIG.  541.— Capacity  of  MiU. 

unit  of  capacity  drops  from  0*35  H.P.  for  a  10,000  klg.  per  day  mill  almost 
to  0-25  H.P.  for  a  mill  with  200,000  klg.  capacity. 

The  diagram,  Fig.  541,  gives  the  power  consumption  of  an  automatic 
rye  mill. 

The  diagrams  examined  represent  the  power  consumption  in  automatic 
high  grinding  mills  according  to  German  data. 

In  Russia  the  motive  power,  depending  on  the  character  of  the  grind- 
ing, is  expressed  in  the  following  table  : 

TABLE  LXV 


Number  of  H.P.  per  1000  Poods 
in  24  Hours. 

Kind  of  Grinding. 

23  H.P. 

Single  grinding 

27    , 

Scoured 

30     , 

Break 

35     , 

Bolted 

40     . 

Sifted 

50     , 

Dressed 

55     , 

High  wheat  , 

It  should  be  noted  here  that  the  power  consumption  for  high  grinding 
includes  also  the  consumption  for  electric  lighting. 


€HAP.    X] 


FLOUR    MILLING 


579 


Number  of  Hands. — A  less  substantial  part  of  the  working  expenses 
constitutes  the  payment  of  the  workmen.  In  an  automatic  mill  that 
expenditure  forms  a  very  small  part  of  the  sum  total  of  working  costs. 


^   Sacking  Mill. 
36 I 


ISOCO        SOO&O 


JOOOOO 

FIG.  542.— Capacity  of  Mill. 


iooooo  *j 


The  diagrams  given  here  represent  the  average  of  hands  in  the 
German  mills. 

Fig.  542  gives  a  diagram  of  the  number  of  hands  in  the  day  shift  for 
the  sacking  and  the  automatic  mills,  and  Fig.  543  the  number  of  hands 
in  the  night  shift. 


Sacking  Mill. 

• """" 


taoooo  n  ». 


FIG.  543.—  Capacity  of  Mill. 


As  we  see  from  the  diagrams,  the  night  shift  demands  a  less  number 
of  hands.  That  is  explained  by  the  fact  that  in  the  night  time  the  work 
of  unloading  the  sacks  out  of  the  mill,  and  often  of  packing  of  the  flour, 
is  discontinued. 


Ill 

SELECTION  OF  A  PRIME  MOTOR 

One  of  the  most  important  questions  in  making  out  a  project  for  a 
mill  is  the  question  of  selecting  a  prime  motor,  since  a  large  part  of  the 
working  expenses  of  the  mill  is  taken  up,  as  we  remarked  above,  by  the 
production  of  motive  power. 


580  FLOUR   MILLING  [CHAP,  x 

When  choosing  a  motor  for  the  engine  plant  one  has  previously  to 
solve  the  question  concerning  its  power,  which  is  found  by  summing 
up  the  total  power  required  by  all  the  mills  and  machines  of  the  given 
plant.  In  some  cases,  when  an  enlargement  of  the  output  is  expected,  to 
the  initial  power  a  reserve  is  added,  which  discounts  the  presupposed 
enlargement.  The  desirability,  and  in  some  plants  the  necessity,  of  a 
reserve  motor  is  also  taken  into  consideration. 

All  the  difficulty,  however,  of  selecting  a  motor  lies  not  in  the  question 
of  the  power  hi  connection  with  the  reserve  motor  or  the  presupposed 
development  of  the  produce,  but  in  the  selection  of  the  type  of  motor. 

The  variety  of  motors  offered  by  modern  technics  makes  the  choice 
of  a  type  of  motor  sometimes  a  rather  difficult  problem.  Besides  the 
questions  of  a  special  character,  connected  with  local  conditions  and 
peculiarities  of  the  given  plant,  there  comes  up  the  question  of  a  correct 
economic  calculation  of  the  working  expenses. 

In  technical  literature  one  is  often  warned  against  drawing  up  general 
formulae  and  recipes,  according  to  which,  in  a  most  simple  manner,  the 
suitability  of  this  or  that  motor  engine  can  be  found.  Nevertheless  the 
attempt  to  generalise  the  data,  which  to  a  certain  degree  elucidate  the 
above-mentioned  questions,  cannot  be  regarded  as  inexpedient. 

At  such  factories — as  some  of  the  chemical  fabrics,  breweries,  and  saw- 
mills, where  besides  the  motive  power  the  engine-house  has  also  to 
supply  the  caloric  energy  for  the  heating  sources  which  serve  for  drying 
and  other  purposes — the  question  concerning  the  selection  of  a  motor 
engine  is  solved  simply  in  favour  of  the  steam  plant,  and  in  these  cases 
the  problem  of  the  economic  calculation  is  considerably  simplified. 

In  such  cases  where  the  power  plant  has  to  supply  only  the  motive 
power,  the  circumstances  resulting  from  local  conditions  and  the  char- 
acter of  production  are  most  essential. 

The  reliability  and  simplicity  of  the  work  must  be  considered,  the 
quantity  of  space  occupied  by  the  engine,  the  possibility  of  enlarging 
the  output,  rapid  starting,  the  possibility  of  overloading  and  of  the  best 
adjustability,  as  well  as  the  danger  involved  in  different  respects  by 
the  operation. 

It  is  evident  that  the  coexistence  of  all  these  conditions  or  even  only 
of  several  in  one  motor  is  impossible,  and  the  solution  has  always  the 
character  of  a  compromise,  it  being  necessary  at  the  same  time  to  reckon 
with  the  working  expenses  of  some  one  or  other  kind  of  plant. 

When  estimating  the  working  expenses,  there  comes  into  relief  the 
question  of  the  uninterrupted  or  intermittent  work  of  the  motor,  which 


CHAP,  x]  FLOUR    MILLING  581 

greatly  influences  the  correlation  of  the  direct  and  indirect  expenses  in 
operation. 

Turning  now  to  the  question  of  summing  up  the  working  expenses,  we 
must  note  that  the  indirect  expenses,  which  consist  of  the  expenses  in 
respect  of  depreciation  of  the  plant  and  of  the  interest  for  the  deduction 
of  the  capital  expended  on  the  plant.  These  are  reckoned  out  in 
each  separate  case  in  accordance  with  the  engine  supplier's  conditions 
of  credit. 

When  choosing  a  motor  it  has  to  be  decided  first  how  many  days  in 
the  year  the  mill  will  be  working,  whether  it  will  run  continuously  day 
and  night  during  the  week,  with  a  halt  on  Sunday,  or  work  days  only. 

To  define  the  efficiency  of  any  particular  motor  one  must  reckon  out  : 
(1)  the  first  cost,  aftd  (2)  the  working  expenses. 

In  calculating  the  first  cost  one  has  to  find  out  : 

1.  The  price  of  ground  occupied  by  the  power  plant. 

2.  The  costs  of  the  power  plant  and  its  outfit. 

3.  The  costs  of  the  motor  and  its  setting,  including  the  costs  of  the 

foundation,  erection,  and  the  trial  starting. 
The  working  expenses  should  be  divided  into  two  groups  : 

A.  Indirect  Expenses,  consisting  of  the  following  classes  : 

1.  Interest  for  the  price  of   the  site  occupied  by  the  power  plant 

(4 1  to  5  per  cent.). 

2.  Interest  on  the  capital  spent  on  the  building  and  full  plant  (4| 

to  6  per  cent.). 

3.  Depreciation  of  the  building  (2J  to  3  per  cent.). 

4.  Depreciation  of  the  plant  (8  to  10  per  cent.). 

5.  Insurance  premium  (2  to  2|  per  cent.). 

6.  Repairs  of  the  building  (J  to  f  per  cent.). 

7.  Repairs  and  upkeep  of  the  plant  (1J  to  2  per  cent.). 

B.  Direct  Expenses 

1.  Cost  of  fuel. 

2.  Engineer  and  the  rest  of  the  staff  attending  the  plant. 

3.  Expenses  in  lubrication  and  cleaning  of  the  plant. 

In  this  way  knowing  the  costs  of  the  plant  and  the  working  expenses,, 
the  efficiency  of  this  or  that  motor  may  be  defined. 

The  main  expenditure  for  an  engine  plant  is  the  cost  of  fuel.  There- 
fore to  decide  upon  the  kind  of  motor  for  the  projected  mill,  one  must 


582  FLOUR    MILLING  [CHAP,  x 

know  the  prices  of  different  fuels.  Further,  one  should  inquire  of  the 
firms  the  price  of  motors  and  boilers  suitable  to  the  given  locality  ; 
if  a  steam  plant  is  in  view,  the  price  of  foundation  for  a  normal 
ground  and  outfit  as  well  as  the  guaranteed  expenses  per  hour-power. 
Having  all  these  data  in  hand,  it  is  easy  to  define  what  motor  will  be  most 
advantageous,  taking  into  consideration  all  direct  and  indirect  expenses. 
When  testing  the  motor  strictest  attention  should  be  paid  that  the 
guaranteed  consumption  of  fuel  is  correct.  For  that  purpose  it  is  best 
to  call  in  a  disinterested  expert,  who  will  subject  the  motor  to  a  trial  and 
test  its  power  and  consumption  of  fuel  per  horse-power  per  hour. 


INDEX 


Accessory  appliances  used  in  mills,  422. 

Alsop  bleaching  process,  480. 

America,  mill  used  by  Indians  in  Ken- 
tucky, 5  ;  automatic  mill  first  used  in, 
23  ;  influence  of  American  methods  in 
Europe,  26 ;  modern  American  roller 
mills,  268  ;  construction  of,  565. 

Arabia,  a  water-mill  described,  17. 

Archimedean  screw,  the,  described,  458. 

Bashkirs,  a  water-mill  used  by  the,  18. 

Bleaching  (flour),  480. 

Building,  mill,  builders  of  the  eighteenth 
century,  27  ;  present-day  construction, 
554 ;  cost  of  building  and  equipping 
modern  mill,  575. 

Caucasus,  milling  methods  of  the  natives,  19. 
Cereals,  chemical  composition  of,  48. 
China,  ancient  mills  and  methods  of  milling, 
5,  15  ;   rice  mills,  10  ;    modern  methods, 

IS- 

Cleansing  (grain),  58  ;  machines  described, 
83  ;  scouring  and  polishing  machines, 

93- 
Cyclones,  427. 

Detachers,  313. 

Drying  (grain)  machinery,  125. 
Dukhobors,  mill  used  by  the,  10. 
Dust-collectors,  426. 

Egypt,    ancient,    milling    apparatus    and 

methods,  3,  6. 
Elevators,  448. 

Equipment  of  mills,  cost  of,  575. 
Exhaust  systems,  434. 

Feed  governor,  described,  478. 
Filters,  429. 

Flour,  mixing,  469  ;    packing,  473  ;  bleach- 
ing, 480. 
France,  modern  mills  and  methods  in,  27. 

Germany,  development  of  milling  in,  29. 


Grain,  chemical  composition  of,  47  ;  separa- 
tion of  foreign  matter  from,  58  ;  scouring 
and  polishing,  93  ;  drying,  125. 

Greece,  ancient,  milling  apparatus  and 
methods,  4. 

Grinding,  machinery,  153. 

Grinding  principle,  antiquity  of  the,  7  ; 
development  of,  1 1 . 

Grindstones,  first  appearance  of,  7  ;  early 
forms,  8  ;  composition  and  design  of 
modern  stones,  160  ;  erection  of,  171. 

Hignett's  stone  separator,  92. 
Hindoos,  type  of  mill  used  by  the,  15. 
Homer,  milling  references,  8. 
Horde's  separator,  75. 
Horizontal  conveyors,  458. 

India,  type  of  mill  used  by  Hindoos,  15. 
Jews,  milling  methods  in  Biblical  days,  7. 

London,  first  steam  mill  in,  27. 
Luther's  stone  separator,  92. 

Magnetic  separators,  59. 

Maize,  grinding  systems,  536 

Mexico,  milling  methods  of  native  Indians, 

6. 
Middlings-    and    Dunst-grading  -machines, 

406. 
Mills,  mill  builders  of  the  eighteenth  century, 

27;      present-day    construction,     554; 

cost  of  erection,  equipment  and  working 

of  modern  mill,  575. 
Millstones  :  see  GRINDSTONES. 
Morocco,  ancient  Egyptian  methods  in,  9. 

Negroes,  present-day  milling  methods  of  the 
Nile  tribes,  4. 

Oatmeal,  grinding  systems,  538. 

Plansifters,  68,  344  ;  capacity  of,  386. 
Pompeii,  type  of  mill  used  in,  13. 


584 


INDEX 


Porcelain  rolls,  212. 
Purifying    machines, 
420. 


392  ;      capacity    of, 


Reel-separators,  64,  336 

Robinson's  cyclo-pneumatic  separator,  74, 

423 
Roller    mills,    37,    209  ;     types    of,    258  ; 

capacity  of,  299  ;  ventilation  of,  434. 
Rolls,  used  in  roller  mills,  described,  210. 
Rome,     ancient,     milling    apparatus    and 

methods  in,  12. 
Rye,  grinding  systems,  527. 

Scales,  476. 

Scouring  machines,  100. 

Seek  Bros.'  aspirator,  78. 

Sieve-bolters,  70. 

Sifting,    described,    61  ;     construction    of 

sifting  machines,  63,  335  ;    sifting  after 

grinding,  316. 
Spouts,  described,  445. 
Steam-mills,  introduction  and  development 

of,  27. 
Stone  mills,  capacity  of,  190. 


Stones  :   see  GRINDSTONES. 
Systems  of  milling,  489. 

Transportation  of  stock,  445. 
Trieurs,  83. 

Under-runner  mills,  183. 
Upper-runner  mills,  190. 

Ventilation  of  mills,  434. 
Vertical  mills,  187. 
Vibro-motor  plansifters,  68. 

Water-mills,  type  of  mill  described  by 
Vitruvius,  16  ;  an  Arabian  mill,  17  ;  a 
Bashkir  mill,  18. 

Wheat,  the  grain  described,  41  ;  chemical 
composition  of,  47  ;  varieties]  of,  48  ; 
composition  of  English  and  m  Scotch 
varieties,  50  ;  of  foreign  varieties,  52  ; 
of  American  varieties,  54. 

Winnowing,  described ;  winnowing  ma- 
chines, 72. 

Zigzag  separator,  80. 


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Brainard,  F.  R.     The  Sextant.     (Science  Series  No.  101.) i6mo, 

Brassey's  Naval  Annual  for   1915.     War  Edition .  ...8vo,  400 

Briggs,  R.,  and  Wolff,  A.  R.     Steam-Heating.     (Science  Series  No. 

68.) i6mo,  o  50 

Bright,  C.     The  Life  Story  of  Sir  Charles  Tilson  Bright 8vo,  *4  50 

Brislee,  T.  J.    Introduction  to  the  Study  of  Fuel.     (Outlines  of  Indus- 
trial Chemistry.) 8vo,  *3  oo 

Broadfoot,  S.  K.    Motors:  Secondary  Batteries.     (Installation  Manuals 

Series.) izmo,  *o  75 

Broughton,  H.  H.    Electric  Cranes  and  Hoists *9  oo 

Brown,  G.    Healthy  Foundations.     (Science  Series  No.  80.) i6mo,  o  50 

Brown,  H.    Irrigation 8vo,  *5  oo 

Brown,  H.    Rubber 8vo,  *2  oo 

W.  A.     Portland  Cement  Industry 8vo,  3  oo 

Brown,    Wm.    N.      Dipping,    Burnishing,    Lacquering    and    Bronzing 

Brass   Ware 1200,  *i  25 

Handbook  on  Japanning i2mo,  *i  50 


6         D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Brown,  Wm.  N.     The  Art  of  Enamelling  on  Metal i2mo,  *i  oo 

House  Decorating  and  Painting i2mo,  *i  50 

. History  of  Decorative  Art i2mo,  *i  25 

. Workshop  Wrinkles 8vo,  *i  oo 

Browne,  C.  L.    Fitting  and  Erecting  of  Engines 8vo,  *i  50 

Browne,  R.  E.     Water  Meters.     (Science  Series  No.  81.) i6mo,  0.50 

Bruce,  E.  M.     Pure  Food  Tests i2mo,  *i  25 

Detection  of  Common  Food  Adulterants i2mo,  i  25 

Brunner,  R.     Manufacture  of  Lubricants,  Shoe  Polishes  and  Leather 

Dressings.     Trans,  by  C.  Salter 8vo,  *3  oo 

Buel,  R.  H.     Safety  Valves.     (Science  Series  No.  21.) i6mo,  o  50 

Bunkley,  J.  W.     Military  and  Naval  Recognition  Book i6mo,  i  oo 

Burley,  G.  W.     Lathes,  Their  Construction  and  Operation i2mo,  i  25 

Burnside,    W.     Bridge    Foundations •; i2mo,  *i  50 

Burstall,  F.  W.    Energy  Diagram  for  Gas.     With  Text 8vo,  i  50 

Diagram.     Sold  separately *i  oo 

Burt,  W.  A.    Key  to  the  Solar  Compass i6mo,  leather,  2  50 

Buskett,   E.  W.     Fire   Assaying i2ino,  *i  25 

Butler,  H.  J.     Motor  Bodies  and  Chassis 8vo,  *2  50 

Byers,  H.  G.,  and  Knight,  H.  G.     Notes  on  Qualitative  Analysis ....  8vo,  *i  50 

Cain,  W.    Brief  Course  in  the  Calculus i2mo,  *i  75 

—  Elastic  Arches.     (Science  Series  No.  48.) i6mo,  o  50 

• Maximum  Stresses.     (Science  Series  No.  38.) i6mo,  o  50 

— —  Practical  Designing  Retaining  of  Walls.     (Science  Series  No.  3.) 

i6mo,  o  50 
— —  Theory   of    Steel-concrete    Arches   and   of   Vaulted     Structures. 

(Science  Series  No.  42.) i6mo,  o  50 

Theory  of  Voussoir  Arches.     (Science  Series  No.  12.) i6mo,  o  50 

—  —  Symbolic  Algebra.     (Science  Series  No.  73.) i6mo,  o  50 

Carpenter,  F.  D.    Geographical  Surveying.    (Science  Series  No.  37.).i6mo, 

Carpenter,  R.  C.,  and  Diederichs,  H.     Internal  Combustion  Engines. .  8vo,  *5  oo 

Carter,  H.  A.    Ramie  (Rhea),  China  Grass i2mo,  *2  oo 

Carter,  H.  R.    Modern  Flax,  Hemp,  and  Jute  Spinning 8vo,  *3  oo 

Bleaching,  Dyeing  and  Finishing  of  Fabrics 8vo,  *i  oo 

Cary,  E.  R.     Solution  of  Railroad  Problems  with  the  Slide  Rule. .  i6mo,  *i  oo 

Casler,  M.  D.    Simplified  Reinforced  Concrete  Mathematics i2mo,  *i  oo 

Cathcart,  W.  L.     Machine  Design.     Part  I.  Fastenings 8vo,  *3  oo 

Cathcart,  W.  L.,  and  Chaff  ee,  J.  I.     Elements  of  Graphic  Statics .  .  .  8vo,  *3  oo 

Short  Course  in  Graphics i2mo,  i  50 

Caven,  R.  M.,  and  Lander,  G.  D.     Systematic  Inorganic  Chemistry. i2mo,  *2  oo 

Chalkley,  A.  P.    Diesel  Engines 8vo,  *4  oo 

Chambers'  Mathematical  Tables 8vo,  i  75 

Chambers,  G.  F.     Astronomy i6mo,  *i  50 

Chappel,  E.    Five  Figure  Mathematical  Tables 8vo,  *2  oo 

Charnock,   Mechanical    Technology 8vo,  *3  oo 

Charpentier,  P.     Timber 8vo,  *6  oo 

Chatley,  H.    Principles  and  Designs  of  Aeroplanes.     (Science  Series 

No.  126) i6mo,  o  50 

How  to  Use  Water  Power I2mo,  *i  oo 

Gyrostatic  Balancing 8vo,  *i  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG          7 

Child,  C.  D.    Electric  Arc 8vo,  *2  oo 

Christian,    M.      Disinfection     and    Disinfectants.      Trans,    by    Chas. 

Salter i2mo,      200 

Christie,  W.  W.     Boiler-waters,  Scale,  Corrosion,  Foaming 8vo,  *3  oo 

—  Chimney  Design  and  Theory 8vo,  *3  oo 

—  Furnace  Draft.     (Science  Series  No.  123.) i6mo,  o  50 

—  Water:  Its  Purification  and  Use  in  the  Industries 8vo,  *2  oo 

Church's  Laboratory  Guide.    Rewritten  by  Edward  Kinch 8vo,  *i  50 

Clapham,  J.  H.     Woolen  and  Worsted  Industries 8vo,  200 

Clapperton,  G.     Practical  Papermaking 8vo,  2  50 

Clark,  A.  G.     Motor  Car  Engineering. 

Vol.    I.     Construction *3  oo 

Vol.  II.    Design 8vo,  *3  oo 

Clark,  C.  H.     Marine  Gas  Engines i2mo,  *i  50 

Clark,  J.  M.     New  System  of  Laying  Out  Railway  Turnouts i2mo,  i  oo 

Clarke,  J.  W.,  and  Scott,  W.    Plumbing  Practice. 

Vol.      I.     Lead  Working  and  Plumbers'  Materials 8vo,  *4  oo 

Vol.    II.    Sanitary  Plumbing  and  Fittings (In  Press.) 

Vol.  III.     Practical  Lead  Working  on  Roofs (In  Press.) 

Clarkson,  R.  B.     Elementary  Electrical  Engineering (In  Press.) 

Clausen-Thue,  W.     A  B   C  Universal  Commercial  Telegraphic   Code. 

Sixth  Edition (In  Press.) 

Clerk,  D.,  and  Idell,  F.  E.     Theory  of  the  Gas  Engine.     (Science  Series 

No.  62.) i6mo,  o  50 

Clevenger,  S.  R.     Treatise  on  the  Method  of  Government  Surveying. 

i6mo,   morocco,  2  50 

Clouth,  F.     Rubber,  Gutta-Percha,  and  Balata 8vo,  *5  o<> 

Cochran,  J.    Concrete  and  Reinforced  Concrete  Specifications 8vo,  *2  50 

Inspection  of  Concrete  Construction 8vo,  *4  oo 

• Treatise  on  Cement  Specifications 8vo,  *i  oo 

Cocking,  W.  C.     Calculations  for  Steel-Frame  Structures i2mo,  *2  25 

Coffin,  J.  H.  C.    Navigation  and  Nautical  Astronomy i2mo,  *3  50 

Colburn,  Z.,  and  Thurston,  R.  H.     Steam  Boiler  Explosions.     (Science 

Series  No.  2.) i6mo,  o  50 

Cole,  R.  S.     Treatise  on  Photographic  Optics i2mo,  i  50 

Coles-Finch,  W.     Water,  Its  Origin  and  Use 8vo,  *5  oo 

Collins,  J.  E.     Useful  Alloys  and  Memoranda  for  Goldsmiths,  Jewelers. 

i6mo,  o  50 

Collis,  A.  G.     High  and  Low  Tension  Switch-Gear  Design 8vo,  *s  50 

Switchgear.      (Installation    Manuals   Series.) i2mo,  *o  50 

Comstock,  D.  F.,  and  Troland,  L.  T.     The  Nature  of  Electricity  and 

Matter  8vo,  *2  oo 

Coombs,  H.  A.     Gear  Teeth.     (Science  Series  No.  120.) i6mo,  o  50 

Cooper,  W.  R.     Primary  Batteries 8vo,  *4  oo 

Copperthwaite,  W.  C.     Tunnel  Shields 4to,  *g  oo 

Corfield,  W.  H.    Dwelling  Houses.     (Science  Series  No.  50.) i6mo,  o  50 

Water  and  Water-Supply.     (Science  Series  No.  17.) i6mo,  o  50 

Cornwall,  H.  B.     Manual  of  Blow-pipe  Analysis 8vo,  *2  50 

Cowee,  G.  A.    Practical  Safety  Methods  and  Devices 8vo,  *3  oo 


8         D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Cowell,  W.  B.    Pure  Air,  Ozone,  and  Water i2mo,  *2  oo 

Craig,  J.  W.,  and  Woodward,  W.  P.     Questions  and  Answers  About 

Electrical  Apparatus i2mo,  leather,  i  50 

Craig,  T.     Motion  of  a  Solid  in  a  Fuel.     (Science  Series  No.  49.) .  i6mo,  o  50 

— -. —  Wave  and  Vortex  Motion.     (Science  Series  No.  43.) i6mo,  o  50 

Cramp,  W.     Continuous  Current  Machine  Design 8vo,  *2  50 

Crehore,  A.  C.     Mystery  of  Matter  and  Energy 8vo,  i  oo 

Creedy,  F.     Single  Phase  Commutator  Motors 8vo,  *2  oo 

Crocker,  F.  B.     Electric  Lighting.     Two  Volumes.     8vo. 

Vol.   I.     The  Generating  Plant 300 

Vol.  II.    Distributing  Systems  and  Lamps 

Crocker,  F.  B.,  and  Arendt,  M.    Electric  Motors 8vo,  *2  50 

Crocker,  F.  B.,  and  Wheeler,  S.  S.    The  Management  of  Electrical  Ma- 
chinery   i2mo,  *i  oo 

Cross,  C.  F.,  Bevan,  E.  J.,  and  Sindall,  R.  W.    Wood  Pulp  and  Its  Applica- 
tions.    (Westminster  Series.) 8vo,  *2  oo 

Crosskey,  L.  R.     Elementary  Perspective 8vo,  i  25 

Crosskey,  L.  R.,  and  Thaw,  J.    Advanced  Perspective 8vo,  i  50 

Culley,  J.  L.    Theory  of  Arches.     (Science  Series  No.  87.) i6mo,  o  50 

Cushing,  H.  C.,  Jr.,  and  Harrison,  N.    Central  Station  Management ...  *2  oo 

Dadourian,  H.  M.    Analytical  Mechanics i2mo,  *3  oo 

Dana,  R.  T.    Handbook  of  Construction  plant i2mo,  leather,  *s  oo 

Danby,  A.    Natural  Rock  Asphalts  and  Bitumens 8vo,  *2  50 

Davenport,  C.     The  Book.     (Westminster  Series.) 8vo,  *2  oo 

Davey,  N.    The  Gas  Turbine 8vo,  *4  oo 

Davies,  F.  H.    Electric  Power  and  Traction 8vo,  *2  oo 

Foundations  and  Machinery  Fixing.     (Installation  Manual  Series.) 

i6mo,  *i  oo 

Deerr,  N.     Sugar  Cane 8vo,  8  oo 

Deite,  C.    Manual  of  Soapmaking.    Trans,  by  S.  T.  King 4to,  *5  oo 

De  la  Coux,  H.    The  Industrial  Uses  of  Water.    Trans,  by  A.  Morris.  8vo,  *4  50 

Del  Mar,  W.  A.    Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.    Deep-level  Mines  of  the  Rand 4to,  *io  oo 

Diamond  Drilling  for  Gold *5  oo 

De  Roos,  J.  D.  C.    Linkages.     (Science  Series  No.  47.) i6mo,  o  50 

Derr,  W.  L.    Block  Signal  Operation Oblong  i2mo,  *i  50 

Maintenance-of-Way  Engineering (In  Preparation.) 

Desaint,  A.    Three  Hundred  Shades  and  How  to  Mix  Them 8vo,  *8  oo 

De  Varona,  A.     Sewer  Gases.     (Science  Series  No.  55.) i6mo,  o  50 

Devey,  R.  G.     Mill  and  Factory  Wiring.     (Installation  Manuals  Series.) 

i2mo,  *i  oo 

Dibdin,  W.  J.     Purification  of  Sewage  and  Water 8vo,  6  50 

Dichmann,  Carl.    Basic  Open-Hearth  Steel  Process i2mo,  *3  50 

Dieterich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins 8vo,  *3  oo 

Dilworth,  E.  C.    Steel  Railway  Bridges 4to.  *4  oo 

Dinger,  Lieut.  H.  C.     Care  and  Operation  of  Naval  Machinery .  . .  i2mo,  *2  oo 
Dixon,  D.  B.    Machinist's  and  Steam  Engineer's  Practical  Calculator. 

i6mo,  morocco,  i  25 
Dodge,  G.  F.    Diagrams  for  Designing  Reinforced  Concrete  Structures, 

folio,  *4  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  9 

Dommett,  W.  E.     Motor  Car  Mechanism i2mo,  *i  50 

Dorr,  B.  F.     The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  morocco,  2  oo 

Draper,  C.  H.     Elementary  Text-book  of  Light,  Heat  and  Sound  .  .  i2mo,  i  oo 

—  Heat  and  the   Principles   of   Thermo-dynamics i2mo,  *2  oo 

Dron,  R.  W.     Mining  Formulas i2mo,  i  oo 

Dubbel,  H.    High  Power  Gas  Engines 8vo,  *s  oo 

Dumesny,  P.,  and  Noyer,  J.     Wood  Products,  Distillates,  and  Extracts. 

8vo,  *4  50 
Duncan,  W.  G.,  and  Penman,  D.     The  Electrical  Equipment  of  Collieries. 

8vo,  *4  oo 

Dunkley,  W.  G.     Design  of  Machine  Elements 8vo,  i  50 

Dunstan,  A.  E.,  and  Thole,  F.  B.  T.     Textbook  of  Practical  Chemistry. 

I2mo,  *i  40 

Durham,  H.  W.     Saws 8vo,  2  50 

Duthie,  A.  L.     Decorative  Glass  Processes.     (Westminster  Series.)  .8vo,  *2  oo 

Dwight,  H.  B.     Transmission  Line  Formulas 8vo,  *2  oo 

Dyson,  S.  S.     Practical  Testing  of  Raw  Materials 8vo,  *5  oo 

Dyson,  S.  S.,  and  Clarkson,  S.  S.     Chemical  Works 8vo,  *7  50 

Eccles,  W.  H.     Wireless  Telegraphy  and  Telephony i2mo,  *4  50 

Eck,  J.     Light,  Radiation  and  Illumination.     Trans,  by  Paul  Hogner, 

8vo,  *2  50 

Eddy,  H.  T.    Maximum  Stresses  under  Concentrated  Loads 8vo,  i  50 

Eddy,  L.  C.    Laboratory  Manual  of  Alternating  Currents i2mo,  o  50 

Edelman,  P.  Inventions  and  Patents i2mo,  *i  50 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments 8vo, 

(In  Press.) 

Edler,  R.     Switches  and  Switchgear.     Trans,  by  Ph.  Laubach .  . .  8vo,  *4  oo 

Eissler,  M.    The  Metallurgy  of  Gold 8vo,  7  50 

The  Metallurgy  of  Silver 8vo,  4  oo 

The  Metallurgy  of  Argentiferous  Lead 8vo,  5  oo 

A  Handbook  on  Modern  Explosives 8vo,  5  oo 

Ekin,  T.  C.    Water  Pipe  and  Sewage  Discharge  Diagrams folio,  *3  oo 

Electric  Light  Carbons,  Manufacture  of 8vo,  i  oo 

Eliot,  C.  W.,  and  Storer,  F.  H.     Compendious  Manual  of  Qualitative 

Chemical  Analysis i2mo,  *i  25 

Ellis,  C.     Hydrogenation  of  Oils 8vo,    (In  Press.) 

Ellis,  G.    Modern  Technical  Drawing 8vo,  *2  oo 

Ennis,  Wm.  D.    Linseed  Oil  and  Other  Seed  Oils 8vo,  *4  oo 

Applied  Thermodynamics 8vo,  *4  50 

Flying  Machines  To-day i2mo,  *i  50 

Vapors  for  Heat  Engines i2mo,  *i  oo 

Ermen,  W.  F.  A.     Materials  Used  in  Sizing 8vo,  *2  oo 

Erwin,  M.     The  Universe  and  the  Atom i2mo,  *2  oo 

Evans,  C.  A.     Macadamized  Roads (In  Press.) 

Ewing,  A,  J,    Magnetic  Induction  in  Iron 8vo,  *4  oo 

Fairie,  J.     Notes  on  Lead  Ores i2mo,  *o  50 

Notes    on   Pottery    Clays "mo,  *i  50 


10       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Fairley,  W.,  and  Andre,  Geo.  J.    Ventilation  of  Coal  Mines.     (Science 

Series  No.  58.) i6mo,  o  50 

Fairweather,  W.  C.  *  Foreign  and  Colonial  Patent  Laws 8vo,  *3  oo 

Falk,  M.  S.     Cement  Mortars  and  Concretes 8vo,  *2  50 

Fanning,  J.  T.    Hydraulic  and  Water-supply  Engineering . 8vo,  *5  oo 

Fay,  I.  W.    The  Coal-tar  Colors 8vo,  *4  oo 

Fernbach,  R.  L.     Glue  and  Gelatine 8vo,  *3  oo 

Firth,  J.  B.    Practical  Physical  Chemistry 12 mo,  *i  oo 

Fischer,  E.    The  Preparation  of  Organic  Compounds.    Trans,  by  R.  V. 

Stanford i2mo,  *i  25 

Fish,  J.  C.  L.    Lettering  of  Working  Drawings Oblong  Svo,  i  oo 

Mathematics  of  the  Paper  Location  of  a  Railroad,  .paper,  i2mo,  *o  25 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing 8vo,  *3  50 

Fleischmann,  W.    The  Book  of  the  Dairy.    Trans,  by  C.  M.  Aikman. 

Svo,  4  oo 
Fleming,  J.  A.    The  Alternate-current  Transformer.     Two  Volumes.  Svo. 

Vol.   I.     The  Induction  of  Electric  Currents *5  oo 

Vol.  II.     The  Utilization  of  Induced  Currents 5  50 

Propagation  of  Electric  Currents Svo,  *s  oo 

— —  A  Handbook  for  the  Electrical  Laboratory  and  Testing  Room.    Two 

Volumes Svo,  each,  *5  oo 

Fleury,  P.    Preparation  and  Uses  of  White  Zinc  Paints Svo,  *2  50 

Flynn,  P.  J.    Flow  of  Water.     (Science  Series  No.  84.) i2mo,  o  50 

Hydraulic  Tables.     (Science  Series  No.  66.) i6mo,  o  50 

Forgie,  J.     Shield  Tunneling Svo.    (In  Press.) 

Foster,  II.  A.     Electrical  Engineers'  Pocket-book.      (Seventh  Edition.) 

i2mo,  leather,  5  oo 

Engineering  Valuation  of  Public  Utilities  and  Factories Svo,  *3  oo 

—  Handbook  of  Electrical  Cost  Data Svo  (In  Press.) 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings . i2mo,  *i  50 

The  Solution  of  Alternating  Current  Problems Svo  (In  Press.) 

Fox,  W.  G.     Transition  Curves.     (Science  Series  No.  no.) i6mo,  o  50 

Fox,  W.,  and  Thomas,  C.  W.     Practical  Course  in  Mechanical  Draw- 
ing   i2mo,  i  25 

Foye,  J.  C.     Chemical  Problems.     (Science  Series  No.  69.) i6mo,  o  50 

Handbook  of  Mineralogy.     (Science  Series  No.  86.) i6mo,  o  50 

Francis,  J.  B.    Lowell  Hydraulic  Experiments 4to,  15  oo 

Franzen,  H.     Exercises  in  Gas  Analysis i2mo,  *i  oo 

Freudemacher,   P.   W.    Electrical   Mining  Installations.     (Installation 

Manuals  Series.) .  .      i2mo,  *i  oo 

Frith,  J.     Alternating  Current  Design Svo,  *2  oo 

Fritsch,  J.    Manufacture  of  Chemical  Manures.    Trans,  by  D.  Grant. 

Svo,  *4  oo 

Frye,  A.  I.     Civil  Engineers'  Pocket-book i2mo,  leather,  *5  oo 

Fuller,  G.  W.     Investigations  into  the  Purification  of  the  Ohio  River. 

4to,  *io  06 

Furnell,  J.    Paints,  Colors,  Oils,  and  Varnishes Svo.  *i  oo 

Gairdner,  J.  W.  I.     Earthwork Svo  {In  Press.) 

Gant,  L.  W.    Elements  of  Electric  Traction .  .    Svo,  *2  50 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  n 

Garcia,  A.  J.  R.  V.     Spanish-English  Railway  Terms 8vo,  *4  50 

Gardner,  H.  A.     Paint  Researches,  and  Their  Practical  Applications, 

8vo,  *s  oo 
Garforth,  W.  E.     Rules  for  Recovering  Coal  Mines  after  Explosions  and 

Fires i2mo,  leather,  i  50 

Garrard,  C.  C.    Electric  Switch  and  Controlling  Gear 8vo,  *6  oo 

Gaudard,  J.     Foundations.     (Science  Series  No.  34.) i6mo,  050 

Gear,  H.  B.,  and  Williams,  P.  F.     Electric  Central  Station  Distribution 

Systems    8vo,  *3  50 

Geerligs,  H.  C.  P.     Cane  Sugar  and  Its  Manufacture 8vo,  *s  oo 

Geikie,  J.     Structural  and  Field  Geology 8vo,  *4  oo 

—  Mountains.     Their   Growth,   Origin   and   Decay r8vo,  *4  oo 

—  The  Antiquity  of  Man  in  Europe ~ 8vo,  *3  oo 

Georgi,  F.,  and  Schubert,  A.     Sheet  Metal  Working.     Trans,  by  C. 

Salter 8vo,  3  oo 

Gerhard,  W.  P.     Sanitation,  Watersupply  and  Sewage  Disposal  of  Country 

Houses i2mo,  *2  oo 

—  Gas  Lighting      (Science  Series  No.  HI.) i6mo,  o  50 

Household  Wastes.     (Science  Series  No.  97.) i6mo,  o  50 

House  Drainage.     (Science  Series  No.  63.) i6mo,  o  50 

- Sanitary  Drainage  of  Buildings.     (Science  Series  No.  93.)           i6mo,  o  50 

Gerhardi,  C.  W.  H.     Electricity  Meters 8vo,  *4  oo 

Geschwind,   L.     Manufacture   of  Alum  and   Sulphates.     Trans,    by  C. 

Salter 8vo,  *s  oo 

Gibbings,  A.  H.     Oil  Fuel  Equipment  for  Locomotives 8vo,  *2  50 

Gibbs,  W.  E.     Lighting  by  Acetylene i2mo,  *i  50 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  *5  oo 

-  Water  Hammer  in  Hydraulic  Pipe  Lines i2mo,  *2  oo 

Gibson,  A.  H.,  and  Ritchie,  E.  G.    Circular  Arc  Bow  Girder 4to,  *3  50 

Gilbreth,  F.  B.     Motion  Study i2mo,  *2  oo 

—  Bricklaying  System    8vo,  *3  oo 

—  Field  System i2mo,  leather,  *3  oo 

—  Primer  of  Scientific  Management i2ino,  *i  oo 

Gillette,  H.  P.     Handbook  of  Cost  Data i2mo,  leather,  *s  oo 

Rock  Excavation  Methods  and  Cost iamo,  *s  oo 

and  Dana,  R.  T.    Cost  Keeping  and  Management  Engineering. 8vo,  *3  50 

—  and  Hill,  C.  S.    Concrete  Construction,  Methods  and  Cost....8vo,  *$  oo 

Gillmore,  Gen.  Q.  A.    Roads,  Streets,  and  Pavements i2mo,  i  25 

Godfrey,  E.     Tables  for  Structural  Engineers i6mo,  leather,  *2  50 

Golding,  H.  A.     The  Theta-Phi  Diagram i2mo,  *i  25 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor 8vo,  *3  oo 

Goodchild,  W.     Precious  Stones.     (Westminster  Series.) 8vo,  *2  oo 

Goodeve,  T.  M.     Textbook  on  the  Steam-engine 12  mo,  2  oo 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  *3  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine i2mo,  i  oo 

Calculus.     (Science  Series  No.  112.) i6mo,  o  50 

High  Masonry  Dams.     (Science  Series  No.  22.) i6mo,  o  50 

Gould,  E.  S.     Practical  Hydrostatics  and  Hydrostatic    Formulas.     (Science 

Series  No.  117.) i6mo,  o  50 


12        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Gratacap,  L.  P.    A  Popular  Guide  to  Minerals 8vo,  *3  oo 

Gray,  J.     Electrical  Influence  Machines. i2mo,  2  oo 

Marine  Boiler  Design "mo,  *i  25 

Greenhill,  G.    Dynamics  of  Mechanical  Flight 8vo,  *2  50 

Gregorius,  R.     Mineral  Waxes.     Trans,  by  C.  Salter i2mo,  *3  oo 

Grierson,  R.    Some  Modern  Methods  of  Ventilation 8vo,  *3  oo 

Griffiths,  A.  B.     A  Treatise  on  Manures i2mo,  3  oo 

Dental  Metallurgy •    -8vo,  *3  5o 

Gross,  E.     Hops 8vo,  *4  So 

Grossman,  J.     Ammonia  and  Its  Compounds i2mo,  *i  25 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases   or  Electricity. 

(Westminster  Series) 8vo,  *2  oo 

Grover,  F.     Modern  Gas  and  Oil  Engines 8vo 

Gruner,  A.     Power-loom  Weaving 8vo,  *3  oo 

Grunsky,  C.  E.     Topographic  Stadia  Surveying .1. . .  i6mo,  2  oo 

Guldner,  Hugo.     Internal  Combustion  Engines.     Trans,  by  H.  Diederichs. 

4to,  *is  oo 

Gunther,  C.  0.     Integration Svo,  *i  25 

Gurden,  R.  L.     Traverse  Tables folio,  half  morocco,  *7  50 

Guy,  A.  E.    Experiments  on  the  Flexure  of  Beams Svo,  *i  25 

Haenig,  A.    Emery  and  Emery  Industry Svo,  *2  50 

Hainbach,  R.     Pottery  Decoration.     Trans,  by  C.  Salter i2mo,  *3  oo 

Hale,  W.  J.     Calculations  of  General  Chemistry i2mo,  *i  oo 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles i2mo,  *2  oo 

Hall,  G.  L.    Elementary  Theory  of  Alternate  Current  Working. .,  .8vo,  *i  50 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  oo 

Hall,  W.  S.     Elements  of  the  Differential  and  Integral  Calculus Svo,  *2  25 

Descriptive  Geometry Svo  volume  and  a  4to  atlas,  *3  50 

Haller,  G.  F.,  and  Cunningham,  E.  T.     The  Tesla  Coil i2mo,  *i  25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

The  Use  of  the  Slide  Rule.     (Science  Series  No.  114.) i6mo,  o  50 

Worm  and  Spiral  Gearing.     (Science  Series  No.  116.) i6mo,  o  50 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics Svo,  i  50 

Hancock,  W.  C.  Refractory  Materials.  (Metallurgy  Series.)   (In  Press.) 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics i2mo,  *i  50 

Haring,  Hi     Engineering  Law. 

Vol.  I.    Law  of  Contract Svo,    *4  oo 

Harper,  J.  H.    Hydraulic  Tables  on  the  Flow  of  Water i6mo,    *2  oo 

Harris,  S.  M.    Practical  Topographical  Surveying (In  Press.) 

Harrison,  W.  B.     The  Mechanics'  Tool-book i2mo,  i  50 

Hart,  J.  W.     External  Plumbing  Work Svo,  *3  oo 

Hints  to  Plumbers  on  Joint  Wiping Svo,  *3  oo 

Principles  of  Hot  Water  Supply Svo,  *3  oo 

Sanitary  Plumbing  and  Drainage Svo,  *3  oo 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hatt,  J.  A/H.     The  Colorist square  i2mo,  *i  50 

Hausbrand,  E.     Drying  by  Means  of  Air  and  Steam.     Trans,  by  A.  C. 

Wright i2mo,  *2  oo 

Evaporating,  Condensing  and  Cooling  Apparatus.     Trans,  by  A.  C. 

Wright Svo,  *5  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  13 

Hausmann,  E.     Telegraph  Engineering 8vo,  *s  oo 

Hausner,  A.     Manufacture  of  Preserved  Foods  and  Sweetmeats.     Trans. 

by  A.  Morris  and  H.  Robson 8vo,  *3  oo 

Hawkesworth,  J.     Graphical  Handbook  for  Reinforced  Concrete  Design. 

4to,  *2  50 

Hay,  A.    Continuous  Current  Engineering 8vo,  *2  50 

Hayes,  H.  V.    Public  Utilities,  Their  Cost  New  and  Depreciation. .  .8vo,  *2  oo 

—  Public  Utilities,  Their  Fair  Present  Value  and  Return 8vo,  *2  oo 

Heath,  F.  H.    Chemistry  of  Photography 8vo.  (In  Press.) 

Heather,  H.  J.  S.    Electrical  Engineering .8vo,  *3  50 

Heaviside,  O.    Electromagnetic  Theory.      Vols.  I  and  II ....  8vo,  each,  *5  oo 

Vol.  Ill 8vo,  *7  50 

Heck,  R.  C.  H.    The  Steam  Engine  and  Turbine 8vo,  *s  50 

Steam-Engine  and  Other  Steam  Motors.    Two  Volumes. 

Vol.    I.     Thermodynamics  and  the  Mechanics 8vo,  *3  50 

Vol.  II.     Form,  Construction,  and  Working 8vo,  *s  oo 

Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Heermann,  P.     Dyers'  Materials.     Trans,  by  A.  C.  Wright i2mo,  *2  50 

Heidenreich,    E.    L.     Engineers'    Pocketbook    of    Reinforced    Concrete, 

i6mo,  leather,  *3  oo 

Hellot,  Macquer  and  D'Apligny.  Art  of  Dyeing  Wool,  Silk  and  Cotton.  8vo,  *2  oo 

Henrici,  O.     Skeleton  Structures 8vo,  i  50 

Bering,  C.,  and  Getman,  F.  H.     Standard  Tables  of  Electro-Chemical 

Equivalents    i2mo,  *i  50 

Hering,  D.  W.    Essentials  of  Physics  for  College  Students 8vo,  *i  75 

Hering-Shaw,  A.     Domestic  Sanitation  and  Plumbing.     Two  Vols. . .  8vo,  *5  oo 

Hering-Shaw,  A.    Elementary  Science 8vo,  *2  oo 

Herington,  C.  F.     Powdered  Coal  as  Fuel 8vo,  3  oo 

Herrmann,  G.     The  Graphical  Statics  of  Mechanism.     Trans,  by  A.  P. 

Smith I2mo,  2  oo 

Herzfeld,  J.     Testing  of  Yarns  and  Textile  Fabrics 8vo,  *3  50 

Hildebrandt,  A.     Airships,  Past  and  Present 8vo,  *3  50 

Hildenbrand,  B.  W.    Cable-Making.     (Science  Series  No.  32.) i6mo,  o  50 

Hilditch,  T.  P.     A  Concise  History  of  Chemistry i2mo,  *i  25 

Hill,  C.  S.     Concrete  Inspection i6mo,  *i  oo 

Hill,  J.  W.    The  Purification  of  Public  Water  Supplies.    New  Edition. 

(In  Press.) 

—  Interpretation  of  Water  Analysis (In  Press.) 

Hill,  M.  J.  M.    The  Theory  of  Proportion 8vo,  *2  50 

Hiroi,  I.    Plate  Girder  Construction.     (Science  Series  No.  95.)  .  . .  i6mo,  o  50 

—  Statically-Indeterminate  Stresses i2mo,  *2  oo 

Hirshfelfi,  C.  F.    Engineering  Thermodynamics.  (Science  Series  No.  45.) 

i6mo,  o  50 

Hoar,  A.     The  Submarine  Torpedo  Boat i2mo,  *2  oo 

Hobart,  H.  M.    Heavy  Electrical  Engineering 8vo,  *4  50 

—  Design  of  Static  Transformers i2mo,  *2  oo 

—  Electricity 8vo,  *2  oo 

Electric  Trains 8vo,  *2  50 

Electric  Propulsion  of  Ships 8vo,  *2  50 


I4       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Hobart,  J.  F.    Hard  Soldering,  Soft  Soldering  and  Brazing i2mo,  *i  oo 

Hobbs,  W.  R.  P.    The  Arithmetic  of  Electrical  Measurements i2mo,  o  75 

Hoff,  J.  N.    Paint  and  Varnish  Facts  and  Formulas i2mo,  *i  50 

Hole,  W.     The  Distribution  of  Gas 8vo,  *7  50 

Holley,  A.  L.    Railway  Practice folio,  6  oo 

Hopkins,  N.  M.    Model  Engines  and  Small  Boats i2mo,  i  25 

Hopkinson,  J.,  Shoolbred,  J.  N.,  and  Day,  R.  E.    Dynamic  Electricity. 

(Science  Series  No.  71.) i6mo,  o  50 

Horner,  J.     Practical  Ironfounding 8vo,  *2  oo 

Gear  Cutting,  in  Theory  and  Practice. 8vo,  *3  oo 

Horniman,  Roy.    How  to  Make  the  Railways  Pay  For  the  War 8vo,  3  oo 

Houghton,  C.  E.    The  Elements  of  Mechanics  of  Materials i2mo,  *2  oo 

Houstoun,  R.  A.    Studies  in  Light  Production i2mo,  2  oo 

Hovenden,  F.     Practical  Mathematics  for  Young  Engineers i2mo,  *i  50 

Howe,  G.     Mathematics  for  the  Practical  Man i2mo,  *i  25 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthenware. 

8vo,  paper,  *o  50 

Hoyt,  W.  E.     Chemistry  by  Experimentation : 8vo,  *o  70 

Hubbard,  E.    The  Utilization  of  Wood-waste 8vo,  *2  oo 

Hiibner,  J.    Bleaching  and  Dyeing  of  Vegetable  and  Fibrous  Materials. 

(Outlines  of  Industrial  Chemistry.) 8vo,  *5  oo 

Hudson,  0.  F.    Iron  and  Steel.    (Outlines  of  Industrial  Chemistry. ).8vo,  *2  oo 
Humphrey,  J.  C.  W.     Metallography  of  Strain.     (Metallurgy  Series.) 

(In  Press.) 

Humphreys,  A.  C.    The  Business  Features  of  Engineering  Practice .  .8 vo,  *i  25 

Hunter,  A.    Bridge  Work 8vo.  (In  Press.) 

Hurst,  G.  H.    Handbook  of  the  Theory  of  Color 8vo,  *2  50 

—  Dictionary  of  Chemicals  and  Raw  Products 8vo,  *4  50 

Lubricating  Oils,  Fats  and  Greases 8vo,  *4  oo 

—  Soaps 8vo,  *5  oo 

Hurst,  G.  H.,  and  Simmons,  W.  H.     Textile  Soaps  and  Oils 8vo,  3  oo 

Hurst,  H.  E.,  and  Lattey,  R.  T.    Text-book  of  Physics 8vo,  *3  oo 

—  Also  published  in  three  parts. 

Part      I.    Dynamics  and  Heat *i  25 

Part    II.    Sound  and  Light *i  25 

Part  III.    Magnetism  and  Electricity *i  50 

Hutchinson,  R.  W.,  Jr.    Long  Distance  Electric  Power  Transmission. 

i2mo,  *3  oo 

Hutchinson,  R.  W.,  Jr.,  and  Thomas,  W.  A.    Electricity  in  Mining.  i2mo, 

(In  Press.) 
Hutchinson,  W.  B.     Patents  and  How  to  Make  Money  Out  of  Them. 

1 2 mo,  i  oo 

Hutton,  W.  S.    The  Works'  Manager's  Handbook 8vo,  6  oo 

Hyde,  E.  W.     Skew  Arches.     (Science  Series  No.  15.) i6mo,  o  50 

Hyde,  F.  S.    Solvents,  Oils,  Gums,  Waxes , , , , 8vo,  *2  oo 

Induction  Coils.     (Science  Series  No.  53.) i6mo,  o  50 

Ingham,  A.  E.    Gearing.    A  practical  treatise 8vo,  *2  50 

Ingle,  H.    Manual  of  Agricultural  Chemistry 8vo,  *3  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  15 

Inness,  C.  H.     Problems  in  Machine  Design I2mo,  *2  oo 

Air  Compressors  and  Blowing  Engines i2mo,  *2  oo 

Centrifugal  Pumps i2mo,  *2  oo 

The  Fan i2mo,  *2  oo 

Jacob,  A.,  and  Gould,  E.  S.  On  the  Designing  and  Construction  of 

Storage  Reservoirs.  (Science  Series  No.  6) i6mo,  o  50 

Jannettaz,  E.  Guide  to  the  Determination  of  Rocks.  Trans,  by  G.  W. 

Plympton i2mo,  i  50 

Jehl,  F.     Manufacture  of  Carbons 8vo,  *4  oo 

Jennings,  A.  S.  Commercial  Paints  and  Painting.  (Westminster  Series.) 

8vo,  *2  oo 

Jennison,  F.  H.     The  Manufacture  of  Lake  Pigments 8vo,  *3  oo 

Jepson,  G.     Cams  and  the  Principles  of  their  Construction 8vo,  *i  50 

Mechanical  Drawing 8vo  (In  Preparation.) 

Jervis-Smich,  F.  J.     Dynamometers. 8vo,  *3  50 

Jockin,  W.     Arithmetic  of  the  Gold  and  Silversmith i2mo,  *i  oo 

Johnson,  J.  H.     Arc  Lamps  and  Accessory  Apparatus.     (Installation 

Manuals  Series.) i2mo,  *o  75 

Johnson,  T.  M.     Ship  Wiring  and  Fitting.     (Installation  Manuals  Series.) 

i2mo,  *o  75 

Johnson,  W.  Me  A.     The  Metallurgy  of  Nickel (In  Preparation.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.     Elements  of  Agricultural  Chemistry 

and  Geology i2mo,  2  60 

Joly,  J.     Radioactivity  and  Geology i2mo,  V3  oo 

Jones,  H.  C.    Electrical  Nature  of  Matter  and  Radioactivity i2mo,  *2  oo 

Nature  of  Solution 8vo,  *3  50 

New  Era  in  Chemistry , zarno,  *2  oo 

Jones,  J.  H      Tinplate  Industry 8vo,  *3  oo 

Jones,  M.  W.     Testing  Raw  Materials  Used  in  Paint i2mo,  *2  oo 

Jordan,  L.  C.     Practical  Railway  Spiral i2mo,  leather,  *i  50 

Joynson,  F.  H      Designing  and  Construction  of  Machine  Gearing  .  .8vo,  2  oo 

J-"ptner,  H.  F.  V.     Siderology:  The  Science  of  Iron 8vo,  *5  oo 

Kapp,  G.     Alternate  Current  Machinery.     (Science  Series  No.  96.). i6mo,  o  50 

Kapper,  F.     Overhead  Transmission  Lines 4to,  *4  oo 

Keim,  A.  W.     Prevention  of  Dampness  in  Buildings 8vo,  *2  oo 

Keller,  S.  S.     Mathematics  for  Engineering  Students.     i2mo,  half  leather. 

—  and  Knox,  W.  E.    Analytical  Geometry  and  Calculus *2  oo 

Kelsey,  W.  R.     Continuous-current  Dynamos  and  Motors 8vo,  *2  50 

Kemble,  W.  T.,  and  Underbill,  C.  R.     The  Periodic  Law  and  the  Hydrogen 

Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F>     Handbook  of  Rocks 8vo,  *i  50 

Kennedy,  A.  B.  W.,  and  Thurston,  R.  H.     Kinematics  of  Machinery. 

(Science  Series  No.  54.) ." i6mo,  o  50 

Kennedy,  A.  B.  W.,  Unwin,  W.  C.,  and  Idell,  F.  E.     Compressed  Air. 

(Science  Series  No.  106.) i6mo,  o  50 


16       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Kennedy,  R.    Electrical  Installations.     Five  Volumes 4to,  15  oo 

Single  Volumes each,  3  50 

—  Flying  Machines;  Practice  and  Design i2mo,  *2  oo 

—  Principles  of  Aeroplane  Construction .8vo,  *i  50 

Kennelly,  A.  E.     Electro-dynamic  Machinery 8vo,  i  50 

Kent,  W.     Strength  of  Materials.     (Science  Series  No.  41.) i6mo,  o  50 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis 8vo,  *2  50 

—  Electrometallurgy.     (Westminster  Series.) .8vo,  *2  oo 

—  The  Electric  Furnace  in  Iron  and  Steel  Production i2mo,  *i  50 

Electro-Thermal   Methods   of  Iron   and   Steel   Production. ..  .8vo,  *s  oo 

Kindelan,  J.    Trackman's  Helper lamo,  2  oo 

Kinzbrunner,  C.     Alternate  Current  Windings 8vo,  *i  50 

—  Continuous  Current  Armatures 8vo,  *i  50 

—  Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kirkaldy,    A..   W.,    and    Evans,    A.    D.      History    and    Economics    of 

Transport 8vo,  *s  oo 

Kirkaldy,  W.  G.    David  Kirkaldy's  System  of  Mechanical  Testing ..  4to,  10  oo 

Kirkbride,  J.     Engraving  for  Illustration 8vo,  *i  50 

Kirkham,  J.  E.     Structural  Engineering 8vo,  *5  oo 

Kirkwood,  J.  P.    Filtration  of  River  Waters 4to,  7  50 

Kirschke,  A.     Gas  and  Oil  Engines i2mo,  *i  25 

Klein,  J.  F.     Design  of  a  High-speed  Steam-engine 8vo,  *s  oo 

—  Physical  Significance  of  Entropy 8vo,  *i  50 

Klingenberg,  G.     Large  Electric   Power   Stations 4to,  *5  oo 

Knight,  R.-Adm.  A.  M.     Modern  Seamanship Svo,  *6  50 

Knott,  C.  G.,  and  Mackay,  J.  S.    Practical  Mathematics . 8vo,  2  oo 

Knox,  G.  D.    Spirit  of  the  Soil lamo,  *i  25 

Knox,  J.     Physico-Chemical  Calculations i2mo,  *i  25           $ 

Fixation  of  Atmospheric  Nitrogen.      (Chemical  Monographs.)  .  i2mo,  *i  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

Hydroelectric  Developments  and  Engineering 4to,  *5  oo 

Koller,  T.     The  Utilization  of  Waste  Products 8vo,  *3  oo 

—  Cosmetics 8vo,  *2  50 

Koppe,  S.  W.    Glycerine i2mo,  *2  50 

Kozmin,  P.  A.     Flour  Milling.     Trans,  by  M.  Falkner 8vo,  7  50 

Kremann,  R.     Application  of  the  Phys.ico-Chemical  Theory  to  Tech- 
nical  Processes   and   Manufacturing   Methods.     Trans,   by  H. 

E.   Potts 8vo,  *s  oo 

Kretchmar,  K.    Yarn  and  Warp  Sizing. 8vo,  *4  oo 

Laff argue,  A.    Attack  in  Trench  Warfare ...,.,,,,,. i6mo,  o  50 

Lallier,  E.  V.    Elementary  Manual  of  the  Steam  Engine i2mo,  *2  oo 

Lambert,  T.     Lead  and  Its  Compounds 8vo,  *3  50 

—  Bone  Products  and  Manures 8vo,  *3  oo 

Lamborn,  L.  L.     Cottonseed  Products 8vo,  *3  oo 

Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 

Lamprecht,  R.     Recovery  Work  After  Pit  Fires.    Trans,  by  C.  Salter .  8vo,  *4  oo 

Lancaster,  M.     Electric  Cooking,  Heating  and  Cleaning 8vo,  *i  oo 

Lanchester,  F.  W.     Aerial  Flight.     Two  Volumes.     8vo. 

Vol.  I.    Aerodynamics *6  oo 

Vol.    II.     Aerodonetics *6  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  [7 

Lanchester,  F.  W.  The  Flying  Machine Svo,  *3  oo 

Lange,  K.  R.  By-Products  of  Coal-Gas  Manufacture i2mo,  2  oo 

Lamer,  E.  T.  Principles  of  Alternating  Currents i2mo.  *i  25 

La  Rue,  B.  F.  Swing  Bridges.  (Science  Series  No.  107.) i6mo,  o  50 

Lassar-Cohn.  Dr.  Modern  Scientific  Chemistry.  Trans,  by  M.  M. 

Pattison  Muir i2mo,  *2  oo 

Latimer,  L.  H.,  Field,  C.  J.,  and  Howell,  J.  W.  Incandescent  Electric 

Lighting.  (Science  Series  No.  57.)  i6mo,  o  50 

Latta,  M.  N.  Handbook  of  American  Gas-Engineering  Practice  .  .  .  Svo,  *4  50 

—  American  Producer  Gas  Practice 4to,  *6  oo 

Laws,  B.  C.    Stability  and  Equilibrium  of  Floating  Bodies Svo,  *3  50 

Lawson,    W.    R.     British    Railways.      A    Financial    and    Commercial 

Survey Svo,  200 

Leask,  A.  R.     Breakdowns  at  Sea i2mo,  2  oo 

— —  Refrigerating  Machinery i2mo,  2  oo 

Lecky,  S.  T.  S.    "Wrinkles"  in  Practical  Navigation Svo,  10  oo 

Le  Doux,  M.     Ice-Making  Machines.     (Science  Series  No.  46.) .  .  i6mo,  o  50 

Leeds,  C.  C.    Mechanical  Drawing  for  Trade  Schools oblong  4to,  *2  oo 

Mechanical  Drawing  for  High  and  Vocational  Schools 4to,  *i  25 

Lefevre,  L.     Architectural  Pottery.     Trans,  by  H.  K.  Bird  and  W.  M. 

Binns ~. .  .4to,  *7  50 

Lehner,  S.     Ink  Manufacture.     Trans,  by  A.  Morris  and  H.  Robson .  Svo,  *2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture Svo,  *i  50 

Letts,  E.  A.     Fundamental  Problems  in  Chemistry Svo,  *2  oo 

Le  Van,  W.  B.    Steam-Engine  Indicator.    (Science  Series  No.  7S.)i6mo,  o  50 

Lewes,  V.  B.     Liquid  and  Gaseous  Fuels.     (Westminster  Series.) .  .Svo,  *2  oo 

—  Carbonization  of  Coal ' Svo,  *3  oo 

Lewis,  L.  P.     Railway  Signal  Engineering Svo,  *3  50 

Lewis  Automatic  Machine  Rifle ;  Operation  of i6mo,  *o  75 


Lieber,  B.  F.     Lieber's  Five  Letter  Standard  Telegraphic  Code... Svo,  *io  oo 
Code.     German  Edition Svo,  *io  oo 

—  Spanish  Edition Svo,  *io  oo 

—  French  Edition Svo,  *io  oo 

—  Terminal  Index Svo,     *2  50 

—  Lieber's  Appendix folio,  *is  oo 

-  Handy  Tables 410,     *2  50 

Bankers  and  Stockbrokers'  Code  and  Merchants  and  Shippers' 

Blank  Tables Svo,  *i$  oo 

—  100,000,000  Combination  Code Svo,  *io  oo 

Engineering  Code Svo,  *i2  50 

Livermore,  V.  P.,  and  Williams,  J.     How  to  Become  a  Competent  Motor- 
man  i2mo,     *i  oo 

Livingstone,  R.     Design  and  Construction  of  Commutators Svo,     *2  25 

Mechanical  Design  and  Construction  of  Generators Svo,     *3  50 

Lloyd,  S.  L.     Fertilizer  Materials (In  Press.) 

Lobben,  P.    Machinists'  and  Draftsmen's  Handbook Svo,      2  50 

Lockwood,  T.  D.     Electricity  ^  Magnetism,  and  Electro-telegraph ....  Svo,      2  50 
Electrical  Measurement  and  the  Galvanometer i2mo,      o  75 


18       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Lodge,  O.  J.  Elementary  Mechanics 12010,  i  50 

— —  Signalling  Across  Space  without  Wires 8vo,  *2  oo 

Loewenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps *4  50 

Lomax,  J.  W.     Cotton  Spinning i2mo,  i  50 

Lord,  R.  T.    Decorative  and  Fancy  Fabrics 8vo,  *3  50 

Loring,  A.  E.    A  Handbook  of  the  Electromagnetic  Telegraph ....  i6mo  o  50 

Handbook.     (Science  Series  No.  39.) i6m,  o  50° 

Lovell,  D.  H.     Practical  Switchwork i2mo,  *i  oo 

Low,  D.  A.    Applied  Mechanics  (Elementary) i6mo,  o  80 

Lubschez,  B.  J.    Perspective i2mo,  *i  50 

Lucke,  C.  E.     Gas  Engine  Design 8vo,  *3  oo 

Power  Plants:   Design,  Efficiency,  and  Power  Costs.     2  vols. 

(In  Preparation.} 

Luckiesh,  M.     Color  and  Its  Application. 8vo,  *s  oo 

—  Light  and  Shade  and  Their  Applications 8vo,  *2  50 

Lunge,  G.     Coal-tar  and  Ammonia.     Three  Volumes 8vo,  *ao  oo 

Technical  Gas  Analysis 8vo,  *4  oo 

Manufacture  of  Sulphuric  Acid  and  Alkali.    Four  Volumes. . .  .8vo, 

Vol.     I.     Sulphuric  Acid.    In  three  parts *i8  oo 

— Vol.  I.     Supplement 8vo,      5  oo 

Vol.  II.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda.    In  two 

parts *i5 .  oo 

Vol.  III.     Ammonia  Soda *io  oo 

Vol.  IV.     Electrolytic  Methods (In  Press.) 

-  Technical  Chemists'  Handbook i2mo,  leather,     *3  50 

-Technical  Methods  of  Chemical  Analysis.    Trans,  by  C.  A.  Keane 
in  collaboration  with  the  corps  of  specialists. 

Vol.     I.     In  two  parts 8vo,  *i5  oo 

Vol.   II.     In  two  parts 8vo,  *i8  oo 

Vol.  III.     In  two  parts 8vo,  *i8  oo 

The  set   (3  vols.)   complete *5o  oo 

Luquer,  L.  M.    Minerals  in  Rock  Sections 8vo,     *i  50 

Macewen,  H.  A.    Pood  Inspection 8vo,  *2  50 

Mackenzie,  N.  F.     Notes  on  Irrigation  Works 8vo,  *2  50 

Mackie,  J.     How  to  Make  a  Woolen  Mill  Pay 8vo,  •  *2  oo 

Maguire,  Wm.  R.     Domestic  Sanitary  Drainage  and  Plumbing  ....  8vo,  4  oo 

Malcolm,  C.  W.    Textbook  on  Graphic  Statics 8vo,  *s  oo 

Malcolm,  H.  W.     Submarine  Telegraph  Cable (In  Press.) 

Mallet,  A.     Compound  Engines.     Trans,  by  R.  R.  Buel.     (Science  Series 

No.  10.) i6mo, 

Mansfield,  A.  N.     Electro-magnets.     (Science  Series  No.  64.)  .  .  .  i6mo,  o  50 

Marks,  E.  C.  R.     Construction  of  Cranes  and  Lifting  Machinery  .  i2mo,  *i  50 

Construction  and  Working  of  Pumps i2mo,  *i  50 

Manufacture  of  Iron  and  Steel  Tubes i2mo,  *2  oo 

Mechanical  Engineering  Materials i2mo,  *i  oo 

Marks,  G.  C.     Hydraulic  Power  Engineering 8vo,  3  50 

—  Inventions,  Patents  and  Designs i?.mo,  *i  oo 

Marlow,  T.  G.     Drying  Machinery  and  Practice 8vo,  *5  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  19 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete 8vo,  *2  50 

— —  Reinforced  Concrete  Compression  Member  Diagram.     Mounted  on 

Cloth  Boards *i .  50 

Marsh,  C.  F.,  and  Dunn,  W.     Manual  of  Reinforced  Concrete  and  Con- 
crete Block  Construction i6mo,  morocco,  *2  50 

Marshall,  W.  J.,  and  Sankey,  H.  R.     Gas  Engines.     (Westminster  Series.) 

8vo,  *2  oo 

Martin,  G.    Triumphs  and  Wonders  of  Modern  Chemistry 8vo,  *2  oo 

—  Modern  Chemistry  and  Its  Wonders 8vo,  *a  oo 

Martin,  N.     Properties  and  Design  of  Reinforced  Concrete i2mo,  *2  50 

Martin,  W.  D.    Hints  to  Engineers i2mo,  *i  50 

Massie,  W.  W.,  and  Underbill,  C.  R.    Wireless  Telegraphy  and  Telephony. 

I2H10,  *I    00 

Mathot,  R.  E.    Internal  Combustion  Engines 8vo,  *4  oo 

Maurice,  W.    Electric  Blasting  Apparatus  and  Explosives 8vo,  *3  50 

- — -  Shot  Firer's  Guide 8vo,  *i  50 

Maxwell,     J.     C.      Matter    and  Motion.       (Science   Series  No.  36.). 

i6mo,  o  50 

Maxwell,  W.  H.,  and  Brown,  J.  T.    Encyclopedia  of  Municipal  and  Sani- 
tary Engineering 4to,  *io  oo 

Mayer,  A.  M.    Lecture  Notes  on  Physics 8vo,  2  oo 

Mayer,  C.,  and  Slippy,  J.  C.    Telephone  Line  Construction 8vo,  *s  oo 

McCullough,  E.    Practical  Surveying i2mo,  *2  oo 

Engineering  Work  in  Cities  and  Towns 8vo,  *$  oo 

—  Reinforced  Concrete    i2mo,  *i  50 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 

McGibbon,  W.  C.    Indicator  Diagrams  for  Marine  Engineers 8vo,  *s  oo 

Marine  Engineers'  Drawing  Book oblong  4to,  *2  50 

McGibbon,  W.  C.     Marine  Engineers  Pocketbook i2mo,  *4  oo 

Mclntosh,  J.  G.    Technology  of  Sugar 8vo,  *5  oo 

—  Industrial  Alcohol 8vo,  *3  oo 

Manufacture  of  Varnishes  and  Kindred  Industries.     Three  Volumes. 

8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling *3  50 

Vol.   II.     Varnish  Materials  and  Oil  Varnish  Making *4  oo 

Vol.  III.     Spirit  Varnishes  and  Materials *4  50 

McKillop,  M.,  and  McKillop,  A.  D.     Efficiency  Methods i2mo,  i  50 

McKnight,  J.  D.,  and  Brown,  A.  W.     Marine  Multitubular  Boilers *i  50 

McMaster,  J.  B.     Bridge  and  Tunnel  Centres.     (Science  Series  No.  20.) 

i6mo,  o  50 

McMechen,  F.  L.     Tests  for  Ores,  Minerals  and  Metals i2mo,  *i  oo 

McPherson,  J.  A.     Water-works  Distribution 8vo,  2  50 

Meade,  A.     Modern  Gas  Works  Practice 8vo,  *7  50 

Meade,   Alwyne.     Modern   Gas  Works   Practice 8vo,  750 

Meade,  R.  K.    Design  and  Equipment  of  Small  Chemical  Laboratories, 

8vo, 

Melick,  C.  W.     Dairy  Laboratory  Guide i2mo,  *i  25 

Mensch,  L.  J.    Reinforced  Concrete  Pocket  Book i6mo,  leather,  *4  oo 

Merck,  E.     Chemical  Reagents;  Their  Purity  and  Tests.     Trans,   by 

H.  E.  Schenck 8vo,  i  oo 

Merivale,  J.  H.     Notes  and  Formulae  for  Mining  Students i2mo,  i  50 


20        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Merritt,  Wm.  H.  Field  Testing  for  Gold  and  Silver i6mo,  leather,  i  50 

Mertens.  Tactics  and  Technique  of  River  Crossings.  Translated  by 

W.  Kruger 8vo,  2  50 

Mierzinski,  S.  Waterproofing  of  Fabrics.  Trans,  by  A.  Morris  and  H. 

Robson 8vo,  *2  50 

Miessner,  B.  F.  Radio  Dynamics i2mo,  *2  oo 

Miller,  G.  A.     Determinants.     (Science  Series  No  105.) i6mo, 

Miller,  W.  J.     Introduction  to  Historical  Geology i2mo,  *2  oo 

Milroy,  M.  E.  W.    Home  Lace-making i2mo,  *i  oo 

Mills,  C.  N.    Elementary  Mechanics- for  Engineers 8vo,  *i  oo 

Mitchell,  C.  A.     Mineral  and  Aerated  Waters 8vo,  *3  oo 

Mitchell,  C.  A.,  and  Prideaux,  R.  M.    Fibres  Used  in  Textile  and  Allied 

Industries . . .  - 8vo,  *3  oo 

Mitchell,  C.  F.,  and  G.  A.    Building  Construction  and  Drawing.     i2mo. 

Elementary  Course .'. *i  50 

Advanced  Course *2  50 

Monckton,  C.  C.  F.     Radiotelegraphy.     (Westminster  Series.) 8vo,  *2  oo 

Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish,  Spanish- 
English  Technical  Terms 64mo,  leather,  *i  oo 

Montgomery,  J.  H.     Electric  Wiring  Specifications i6mo,  *i  oo 

Moore,  E.  C.  S.     New  Tables  for  the  Complete  Solution  of  Ganguillet  and 

Kutter's  Formula 8vo,  *5  oo 

Morecroft,  J.  H.,  and  Hehre,  F.  W.     Short  Course  in  Electrical  Testing. 

8vo,  *i  50 

Morgan^  A.  P.     Wireless  Telegraph  Apparatus  for  Amateurs i2mo,  *i  50 

Moses,  A.  J.     The  Characters  of  Crystals 8vo,  *2  oo 

and  Parsons,  C.  L.    Elements  of  Mineralogy 8vo,  *s  oo 

Moss,  S.A.  Elements  of  Gas  Engine  Design. (Science  Series  No.  121. )i6mo,  o  50 

The  Lay-out  of  Corliss  Valve  Gears.     (Science  Series  No.  H9.)i6mo,  o  50 

Mulford,  A.  C.    Boundaries  and  Landmarks i2mo,  *i  oo 

Mullin,  J.  P.    Modern  Moulding  and  Pattern-making i2mo,  2  50 

Munby,  A.  E.     Chemistry  and  Physics  of  Building  Materials.     (West- 
minster Series.) 8vo,  *2  oo 

Murphy,  J.  G.    Practical  Mining i6mo,  i  oo 

Murray,  J,  A,    Soils  and  Manures,    (Westminster  Series.) 8vo,  *2  oo 

Nasmith,  J.    The  Student's  Cotton  Spinning 8vo,  3  oo 

Recent  Cotton  Mill  Construction I2mo,  2  50 

Neave,  G.  B.,  and  Heilbron,  I.  M.    Identification  of  Organic  Compounds. 

i2mo,  *i  25 

Neilson,  R.  M.    Aeroplane  Patents 8vo,  *2  oo 

Nerz,  F.     Searchlights.    Trans,  by  C.  Rodgers 8vo,  *3  oo 

Neuberger,  H.,  and  Noalhat,  H.    Technology  of  Petroleum.     Trans,  by 

J.  G.  Mclntosh 8vo,  *io  oo 

Newall,  J.  W.    Drawing,  Sizing  and  Cutting  Bevel-gears 8vo,  i  50 

Newell,  F.  H.,  and  Drayer,  C.  E.    Engineering  as  a  Career.  .i2mo,  cloth,  *i  oo 

paper,  o  75 

Newbeging,  T.    Handbook  for  Gas  Engineers  and  Managers 8vo,  *6  50 

Nicol,  G.     Ship  Construction  and  Calculations 8vo,  *5  oo 

Nipher,  F.  E.    Theory  of  Magnetic  Measurements I2mo,  i  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG       21 

Nisbet,  H.     Grammar  of  Textile  Design 8vo,  *s  oo 

Nolan,  H.     The  Telescope.     (Science  Series  No.  51.) i6mo,  o  50 

North,  H.  B.    Laboratory  Experiments  in  General  Chemistry i2mo,  *i  oo 

Nugent,  E.     Treatise  on  Optics i2mo,  i  50 

O'Connor,  H.     The  Gas  Engineer's  Pocketbook i2mo,  leather,  3  50 

Ohm,  G.  S.,  and  Lockwood,  T.  D.     Galvanic  Circuit.     Translated  by 

William  Francis.     (Science  Series  No.  102.) i6mo,  o  50 

Olsen,  J.  C.     Text-book  of  Quantitative  Chemical  Analysis 8vo,  3  50 

Olsson,  A.     Motor  Control,  in  Turret  Turning  and  Gun  Elevating.     (U.  S. 

Navy  Electrical  Series,  No.  i.) .' i2mo,  paper,  *o  50 

Ormsby,  M.  T.  M.     Surveying xarno,  i  50 

Oudin,  M.  A.     Standard  Polyphase  Apparatus  and  Systems 8vo,  *3  oo 

Owen,  D.     Recent  Physical  Research 8vo,  *i  50 

Pakes,  W.  C.  C.,  and  Nankivell,  A.  T.    The  Science  of  Hygiene  .  .8vo,  *i  75 

Palaz,  A.     Industrial  Photometry.     Trans,  by  G.  W.  Patterson,  Jr .  .  8vo,  *4  oo 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parker,  P.  A.  M.     The  Control  of  Water 8vo,  *5  oo 

Parr,  G.  D.  A.     Electrical  Engineering  Measuring  Instruments. ..  .8vo,  *s  50 
Parry,   E.  J.     Chemistry  of  Essential  Oils  and  Artificial   Perfumes, 

(In  Press.) 
Foods  and  Drugs.     Two  Volumes. 

Vol.   I.    Chemical  and  Microscopical  Analysis  of  Foods  and  Drugs.  *7  50 

Vol.  H.    Sale  of  Food  and  Drugs  Act *3  oo 

and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *4  50 

Parry,  L.    Notes  on  Alloys 8vo,  *s  oo 

Metalliferous  Wastes   8vo,  *2  oo 

Analysis  of  Ashes  and  Alloys 8vo,  *2  oo 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  oo 

Parshall,  H.  F.,  and  Hobart,  H.  M.     Armature  Windings 4to,  *7  50 

Electric  Railway  Engineering 4to,  *io  oo 

Parsons,  J.  L.     Land  Drainage 8vo,  *i  50 

Parsons,  S.  J.     Malleable  Cast  Iron 8vo,  *2  50 

Partington,  J.  R.    Higher  Mathematics  for  Chemical  Students.  .i2mo,  *2  oo 
Textbook  of  Thermodynamics ! 8vo,  *4  oo 

Passmore,  A.  C.     Technical  Terms  Used  in  Architecture 8vo,  *3  50 

Patchell,  W.  H.    Electric  Power  in  Mines 8vo,  *4  oo 

Paterson,  G.  W.  L.    Wiring  Calculations i2mo,  *2  oo 

Electric  Mine  Signalling  Installations i2mo,  *i  50 

Patterson,  D.     The  Color  Printing  of  Carpet  Yarns 8vo,  *3  50 

Color  Matching  on  Textiles 8vo,  *3  oo 

Textile  Color  Mixing 8vo,  *s  oo 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare  Pipes . .  8vo,  *2  oo 

Transmission  of  Heat  through  Cold-storage  Insulation i2mo,  *i  oo 

Payne,  D.  W.     Iron  Founders'  Handbook 8vo,  *4  oo 

Peckham,  S.  F.     Solid  Bitumens 8vo,  *$  oo 

Peddle,  R.  A.    Engineering  and  Metallurgical  Books i2mo,  *i  50 

Peirce,  B.     System  of  Analytic  Mechanics 410,  10  oo 

Linnear   Associative  Algebra 4to,  3  oo 

Pendred,  V.     The  Railway  Locomotive.     (Westminster  Series.) 8vo,  *2  oo 


22        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Perkin,  F.  M.    Practical  Methods  of  Inorganic  Chemistry i2mo,  *i  oo 

Perrin,  J.     Atoms 8vo,  *2  50 

and  Jaggers,  E.  M.     Elementary  Chemistry i2mo,  *i  oo 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution 8vo,  *3  50 

Petit,  G,     White  Lead  and  Zinc  White  Paints 8vo,  *i  50 

Petit,  R.     How  to  Build  an  Aeroplane.     Trans,  by  T.  O'B.  Hubbard,  and 

J.  H.  Ledeboer 8vo,  *i  50 

Pettit,  Lieut.  J.  S.     Graphic  Processes.     (Science  Series  No.  76.) . . .  i6mo,  o  53 
Philbrick,  P.  H.     Beams  and  Girders.     (Science  Series  No.  88.) , .  .  i6mo, 

Phillips,  J.    Gold  Assaying 8vo,  *2  50 

Dangerous  Goods > 8vo,  3  50 

Phin,  J.     Seven  Follies  of  Science 12010,  *i  25 

Pickworth,  C.  N.     The  Indicator  Handbook.     Two  Volumes.  .i2mo,  each,  i  50 

Logarithms  for  Beginners i2mo.  boards,  o  50 

The  Slide  Rule i2tno,  i  oo 

Plattner's  Manual  of  Blow-pipe  Analysis.    Eighth  Edition,  revised.    Trans. 

by  H.  B.  Cornwall 8vo,  *4  oo 

Plympton,  G.  W.    The  Aneroid  Barometer.    (Science  Series  No.  35.)   i6mo,  o  50 

How  to  become  an  Engineer.     (Science  Series  No.  100.) i6mo,  o  50 

Van  Nostrand's  Table  Book.     (Science  Series  No.  104.) i6mo,  o  50 

Pochet,  M.  L.     Steam  Injectors.     Translated  from  the  French.     (Science 

Series  No.  29.) i6mo,  o  50 

Pocket  Logarithms  to  Four  Places.     (Science  Series  No.  65.) i6mo,  o  50 

leather,  i  oo 

Polleyn,  F.     Dressings  and  Finishings  for  Textile  Fabrics 8vo,  *3  oo 

Pope,  F.  G.    Organic  Chemistry 12010,  *2  25 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph 8vo,  i  50 

Popplewell,  W.  C.     Prevention  of  Smoke 8vo,  *3  50 

Strength  of  Materials 8vo,  *i  75 

Porritt,  B.   D.     The   Chemistry   of   Rubber.      (Chemical   Monographs, 

No.  3.) i2mo,  *i  oo 

Porter,  J.  R.    Helicopter  Flying  Machine 12010,  *i  25 

Potts,  H.  E.     Chemistry  of  the  Rubber  Industry.     (Outlines  of  Indus- 
trial  Chemistry) 8vo,  *2  50 

Practical  Compounding  of  Oils,  Tallow  and  Grease 8vo,  *3  50 

Pratt,  K.     Boiler  Draught i2mo,  *i  25 

High  Speed  Steam   Engines 8vo,  *2  oo 

Pray,  T.,  Jr.     Twenty  Years  with  the  Indicator 8vo,  2  50 

—  Steam  Tables  and  Engine  Constant 8vo,  2  oo 

Prelini,  C.     Earth  and  Rock  Excavation 8vo,  *3  oo 

Graphical  Determination  of  Earth  Slopes 8vo,  *2  oo 

• Tunneling.    New  Edition 8vo,  *3  oo 

Dredging.    A  Practical  Treatise 8vo,  *3  oo 

Prescott,  A.  B.     Organic  Analysis 8vo,  5  oo 

Prescott,  A.  B.,  and  Johnson,  O.  C.     Qualitative  Chemical  Analysis.    .8vo,  *3  50 
Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative  Chemistry. 

I2H10,  *i     50 

Prideaux,  E.  B.  R.    Problems  in  Physical  Chemistry 8vo,  *2  oo 

Primrose,  G.  S.  C.     Zinc.     (Metallurgy  Series.) (In  Press.) 

Prince,  G.  T.    Flow  of  Water ..i2mo,  *2  oo 


D.  VAN  NOSTRAXD  CO.'S  SHORT  TITLE  CATALOG       23 


W.  W.  F.     Application  of  firanhic  Methods  to  the  Design  of 

Structures  .............  :  ............................  12010,  *2  50 

--  Injectors:  Theory,  Construction  and  Working  ...............  izmo,  *i  50 

Diagrams    ......  .  .  .......  .  .....  ......  ___  ..  ........  8ro,  **  50 

...                                           -v:.  *i  50 

Putsch.  A.     Gas  and  Coal-dust  Firing  ............................  STO,  *3  oo 

Pyncbon,  T.  R.    Introduction  to  Chemical  Physics  ................  8ro,  300 

Rafter  G.  W     Mechanics  of  Ventilation.    (<v-5»«»«-»  Series  Bo.  33.)  16010,  o  50 

-  Pntiolr  Water.     »  Science  f?*nfff  Ho.  103.)  .................  1600,  o  50 

-  Treatment  of  Septic  Sewage.     (Science  Series  Ho.  118.)  .  .  .  xonto,  o  50 
Batter,  G.W.,  and  Baker,  M.H.    Sewage  Disposal  in  the  United  States. 

4to,  *6oo 

Raikes,H.P.    Sewage  Disposal  Works  ..........................  STO,  *4  oo 

P.    Enuneb  and  Enamelling  ...................             .  STO,  *4  oo 

Civil  Engineering  .........................................  STO,  6  50 

nr«*fcs«^j  ajud  MUtwork  ...................................  Svo,  5  oo 

r.J.nL,andBamber,K.F.    AntenanUTezt^oolL....^ 

«»«,  3  5» 

Kasck,  £.    Qectoc  Arc  PlMnontena.    Trans,  by  K.  Xoraberg.  .  .....  STO,  *a  oo 

&>o  *i  50 

F.     The  Theory  of  the  Recoil  of  Guns  ............  8vo»  *4  50 

Pan  L  Machine  Drafting  ....................             ........  810,  *i  25 

Part  IL  ic^r^^i  Des%n  ....................  (/«  fVtnaiofion  ) 

Recipes  for  the  Color,  Paint,  Varnish,  CM^  Soan  and  Djrysattin  y  Trades..  Si^  *3  S* 

Recipes  for  Ffint  Glass  Making  ____  ..  .....  .....   ___  ....  .....  .  _  12000,  *4  50 

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24       D-  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Reinhardt,  C.  W.    The  Technic  of  Mechanical  Drafting, 

oblong,  4to,  boards,  *i  oo 
Reiser,  F.     Hardening  and  Tempering  of  Steel.     Trans,  by  A.  Morris  and 

H.  Robson i2mo,  *2  50 

Reiser,  N.     Faults  in  the  Manufacture  of  Woolen  Goods.     Trans,  by  A. 

Morris  and  H.  Robson 8vo,  *2  50 

—  Spinning  and  Weaving  Calculations 8vo,  *5  oo 

Renwick,  W.  G.     Marble  and  Marble  Working 8vo,  5  oo 

Reuleaux,  F.     The  Constructor.    Trans,  by  H.  H.  Suplee 4to,  *4  oo 

Reuterdahl,  A.    Theory  and  Design  of  Reinforced  Concrete  Arches. 8vo,  *2  oo 

Rey,  Jean.     The  Range  of  Electric  Searchlight  Projectors 8vo,  *4  50 

Reynolds,   0.,   and   Idell,   F.   E.     Triple   Expansion   Engines.     (Science 

Series  No.  90.) i6mo,  o  50 

Rhead,  G.  F.     Simple  Structural  Woodwork i2mo,  *i  oo 

Rhodes,  H.  J.     Art  of  Lithography 8vo,  3  50 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining  the  Differ- 
ential of  Functions i2mo,  *  o  50 

Richards,  W.  A.     Forging  of  Iron  and  Steel i2mo,  i  50 

Richards,  W.  A.,  and  North,  H.  B.    Manual  of  Cement  Testing i2mo,  *i  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity i2mo,  *2  oo 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *4  oo 

Rimmer,  E.  J.    Boiler  Explosions,  Collapses  and  Mishaps 8vo,  *i  75 

Rings,  F.     Concrete  in  Theory  and  Practice i2mo,  *2  50 

Reinforced  Concrete  Bridges 4to,  *5  oo 

Ripper,  W.     Course  of  Instruction  in  Machine  Drawing folio,  *6  oo 

Roberts,  F.  C.     Figure  of  the  Earth.     (Science  Series  No.  79.) ij5mo,  o  50 

Roberts,  J.,  Jr.     Laboratory  Work  in  Electrical  Engineering 8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers 8vo,  2  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels.     (Science 

Series  No.  24.) i6mo,  o  5c 

Railroad  Economics.     (Science  Series  No.  59.) i6mo,  o  50 

-  Wrought  Iron  Bridge  Members.     (Science  Series  No.  60.) i6mo,  o  50 

Robson,  J.  H.     Machine  Drawing  and  Sketching 8vo,  *i  50 

Roebling,  J.  A.    Long  and  Short  Span  Railway  Bridges folio,  25  oo 

Rogers,  A.     A  Laboratory;  Guide  of  Industrial  Chemistry 8vo,  2  oo 

. Elements    of   Industrial    Chemistry i2mo,  *s  oo 

Manual  of  Industrial  Chemistry 8vo,  *s  oo 

Rogers,  F.     Magnetism  of  Iron  Vessels.     (Science  Series  No.  30.).  i6mo,  o  So 
Rohland,  P.     Colloidal  and  Crystalloidal  State  of  Matter.     Trans,  by 

W.  J.  Britland  and  H.  E.  Potts i2mo,  *i  25 

Rollinson,  C.    Alphabets Oblong,  i2mo,  *i  oo 

Rose,  J.    The  Pattern-makers'  Assistant 8vo,  2  50 

• Key  to  Engines  and  Engine-running i2mo,  2  50 

Rose,  T.  K.    The  Precious  Metals.     (Westminster  Series.) 8vo,  *2  oo 

Rosenhain,  W.     Glass  Manufacture.     (Westminster  Series.) 8vo,  *2  oo 

Physical  Metallurgy,  An  Introduction  to.     (Metallurgy  Series.) 

8vo,  *3  50 

Roth,   W.   A.     Physical   Chemistry 8vo,  *2  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG       25 

Rowan,  F.  J.    Practical  Physics  of  the  Modern  Steam-boiler 8vo,  *s  oo 

and   Idell,   F.   E.     Boiler  Incrustation  and  Corrosion.      (Science 

Series  No.  27.) i6mo,  050 

Roxburgh,  W.    General  Foundry  Practice.     (Westminster  Series.)  .8vo,  *2  oo 

Ruhmer,  E.    Wireless  Telephony.    Trans,  by  J.  Erskine-Murray . .  8vo,  *3  50 

Russell,  A.    Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Rutley,  F.     Elements  of  Mineralogy i2mo,  *i  25 

Sanford,  P.  G.    Nitro-explosives 8vo,  *4  oo 

Saunders,  C.  H.    Handbook  of  Practical  Mechanics i6mo,  i  oo 

leather,  i  25 

Sayers,  H.  M.    Brakes  for  Tram  Cars 8vo,  *i  25 

Scheele,  C.  W.     Chemical  Essays 8vo,  *2  oo 

Scheithauer,    W.     Shale    Oils    and    Tars 8vo,  *3  So 

Scherer,  R.     Casein.     Trans,  by  C.  Salter 8vo,  *3  oo 

Schidrowitz,  P.     Rubber,  Its  Production  and  Industrial  Uses 8vo,  *5  oo 

Schindler,  K.     Iron  and  Steel  Construction  Works i2mo,  *i  25 

Schmall,  C.  N.    First  Course  in  Analytic  Geometry,  Plane  and  Solid. 

I2mo,  half  leather,  *i  75 

Schmeer,  L.    Flow  of  Water 8vo,  *3  oo 

Schumann,  F.    A  Manual  of  Heating  and  Ventilation. ..  .i2mo,  leather,  i  50 

Schwarz,  E.  H.  L.    Causal  Geology 8vo,  *2  50 

Schweizer,  V.     Distillation  of  Resins 8vo,  4  50 

Scott,  W.  W.     Qualitative  Analysis.    A  Laboratory  Manual 8vo,  *i  50 

Standard   Methods   of   Chemical    Analysis. 8vo,  *6  oo 

Scribner,  J.  M.    Engineers'  and  Mechanics'  Companion.  .i6mo,  leather,  i  50 
Scudder,   H.     Electrical    Conductivity    and   lonization   Constants   of 

Organic  Compounds 8vo,  *s  oo 

Searle,  A.  B.     Modern  Brickmaking 8vo,  *5  oo 

Cement,  Concrete  and  Bricks 8vo,  *s  oo 

Searle,    G.    M.      "Sumners'    Method."      Condensed    and    Improved. 

(Science  Series  No.   124.) i6mo,  o  50 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo  8  oo 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.    Pocket-book  of  Marine  Engi- 
neering  i6mo,  leather,  3  50 

Seeligmann,  T.,  Torrilhon,  G.  L.,  and  Falconnet,  H.    India  Rubber  and 

Gutta  Percha.     Trans,  by  J.  G.  Mclntosh 8vo,  *$  oo 

Seidell,  A.     Solubilities  of  Inorganic  and  Organic  Substances 8vo,  4  50 

Seligman,   R.     Aluminum.      (Metallurgy   Series.) (In  Press.) 

Sellew,  W.  H.     Steel  Rails 4to,  *io  oo 

Railway   Maintenance   Engineering i2mo,  *2  50 

Senter,  G.     Outlines  of  Physical  Chemistry i2mo,  *i  75 

. Text-book  of  Inorganic  Chemistry i2mo,  *i  75 

Sever,  G.  F.    Electric  Engineering  Experiments 8vo,  boards,  *i  oo 

Sever,  G.  F.,  and  Townsend,  F.    Laboratory  and  Factory  Tests  in  Elec- 
trical Engineering 8vo,  *2  50 

Sewall,  C.  H.    Wireless  Telegraphy 8vo,  *2  oo 

Lessons  in  Telegraphy i2mo,  *i  oo 


26       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Sewell,  T.     The  Construction  of  Dynamos 8vo,  *s  oo 

Sexton,  A.  H.    Fuel  and  Refractory  Materials izmo,  *a  50 

—  Chemistry  of  the  Materials  of  Engineering lamo,  *2  50 

Alloys  (Non-Ferrous) 8vo,  *3  oo 

Sexton,  A.  H.,  and  Primrose,  J.  S.  G.  The  Metallurgy  of  Iron  and  Steel. 

8vo,  *6  50 

Seymour,  A.     Modern  Printing  Inks 8vo,  *2  oo 

Shaw,  Henry  S.  H.    Mechanical  Integrators.    (Science  Series  No.  83.) 

i6mo,  o  50 

Shaw,  S.    History  of  the  Staffordshire  Potteries 8vo,  2  oo 

Chemistry  of  Compounds  Used  in  Porcelain  Manufacture.  ..  .8vo,  *5  oo 

Shaw,  T.  R.    Driving  of  Machine  Tools i2mo,  *2  oo 

Shaw,  W.  N.     Forecasting  Weather .8vo,  *s  50 

Sheldon,  S.,  and  Hausmann,  E.    Direct  Current  Machines i2mo,  *2  50 

—  Alternating  Current  Machines i2mo,  *2  50 

Sheldon,  S.,  and  Hausmann,  E.     Electric  Traction  and  Transmission 

Engineering i2mo,  *2  50 

Physical  Laboratory  Experiments,  for  Engineering  Students.  .8vo,  *i  25 

Shields,  J.  E.     Notes  on  Engineering  Construction MHIO,  i  50 

Shreve,  S.  H.     Strength  of  Bridges  and  Roofs 8vo,  3  50 

Slmnk,  W.  F.     The  Field  Engineer i2mo,  morocco,  2  50 

Simmons,  W.  H.,  and  Appleton,  H.  A.    Handbook  of  Soap  Manufacture, 

8vo,  *3  oo 

Simmons,  W.  H.,  and  Mitchell,  C.  A.    Edible  Fats  and  Oils 8vo,  *3  oo 

Simpson,  G.     The  Naval  Constructor i2mo,  morocco,  *5  oo 

Simpson,  W.    Foundations 8vo.   (In  Press.) 

Sinclair,  A.     Development  of  the  Locomotive  Engine. . .  8vo,  half  leather,  5  oo 

Sindall,  R.  W.    Manufacture  of  Paper.     (Westminster  Series.). ..  .8vo,  *2  oo 

Sindall,  R.  W.,  and  Bacon,  W.  N.     The  Testing  of  Wood  Pulp 8vo,  *2  50 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations I2mo,  *2  oo 

Smallwood,  J.  C.     Mechanical  Laboratory  Methods.     (Van  Nostrand's 

Textbooks.)    i2mo,   leather,  *2  50 

Smith,  C.  A.  M.     Handbook  of  Testing,  MATERIALS 8vo,  *2  50 

Smith,  C.  A.  M.,  and  Warren,  A.  G.     New  Steam  Tables 8vo,  *i  25 

Smith,  C.  F.    Practical  Alternating  Currents  and  Testing 8vo,  *2  50 

Practical  Testing  of  Dynamos  and  Motors 8vo,  *2  oo 

Smith,  F.  A.     Railway  Curves i2mo,  *    oo 

—  Standard  Turnou  ts   on  American  Railroads i2mo,  *    oo 

Maintenance   of  Way  Standards i2mo,  *    50 

Smith,  F.  E.    Handbook  of  General  Instruction  for  Mechanics .  .  .  i2mo,  50 

Smith,  H.  G.    Minerals  and  the  Microscope i2mo,  *    25 

Smith,  J.  C.     Manufacture  of  Paint 8vo,  *3  50 

Smith,  R.  H.     Principles  of  Machine  Work i2mo, 

—  Advanced  Machine  Work i2mo,  *3  oo 

Smith,  W.     Chemistry  of  Hat  Manufacturing i2mo,  *3  oo 

Snell,    A.    T.     Electric    Motive  Power 8vo,  *4  oo 

Snow,  W.  G.     Pocketbook  of  Steam  Heating  and  Ventilation.    (In  Press.) 
Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings.     (Science  Series 

No.  5.) i6mo,  o  50 

Soddy,  F.    Radioactivity 8vo,  *3  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  27 

Solomon,  M.    Electric  Lamps.     (Westminster  Series.") 8vo,  *2  oo 

Soraerscales,  A.  N.     Mechanics  for  Marine  Engineers i2mo,  *2  oo 

—  Mechanical  and  Marine  Engineering  Science 8vo,  *5  oo 

Sothern,  J.  W.    The  Marine  Steam  Turbine 8vo,  *6  oo 

—  Verbal  Notes  and  Sketches  for  Marine  Engineers 8vo,  *7  50 

Sothern,   J.   W.,   and   Sothern,   R.   M.     Elementary  Mathematics   for 

Marine    Engineers i2mo,  *i  50 

Simple  Problems  in  Marine  Engineering  Design 12 mo,  *i  50 

Southcombe,  J.  E.     Chemistry  of  the  Oil  Industries.     (Outlines  of  In- 
dustrial Chemistry.) 8vo,  *3  oo 

Soxhlet,  D.  H.     Dyeing  and  Staining  Marble.     Trans,  by  A.  Morris  and 

H.  Robson 8vo,  *2  50 

Spangenburg,  L.     Fatigue  of  Metals.     Translated  by  S.   H.   Shreve. 

(Science  Series  No.  23.) i6mo,  o  50 

Specht,  G.  J.,  Hardy,  A.  S.,  McMaster,  J.  B.,  and  Walling.   Topographical 

Surveying.     (Science  Series  No.  72.) i6mo,  o  50 

Spencer,  A.  S.     Design  of  Steel-Framed  Sheds 8vo,  *3  50 

Speyers,  C.  L.     Text-book  of  Physical  Chemistry 8vo,  *i  50 

Spiegel,  L.    Chemical  Constitution  and  Physiological  Action.     (  Trans. 

by  C.  Luedeking  and  A.  C.  Boylston.) i2mo,  *i  25 

Sprague,   E.   H.     Hydraulics i2mo,  i  50 

Elements   of    Graphic   Statics 8vo,  2  oo 

—  Stability  of  Masonry i2mo,  i  50 

Elementary  Mathematics   for   Engineers i2mo,  *i  50 

Stahl,  A.  W.     Transmission  of  Power.     (Science  Series  No.  28.)  .  i6mo, 

Stahl,  A.  W.,  and  Woods,  A.  T.     Elementary  Mechanism i2mo,  *2  oo 

Staley,  C.,  and  Pierson,  G.  S.     The  Separate  System  of  Sewerage. .  .8vo,  *3  oo 

Standage,  H.  C.    Leatherworkers'  Manual 8vo,  *3  50 

Sealing  Waxes,  Wafers,  and  Other  Adhesives 8vo,  *2  oo 

Agglutinants  of  all  Kinds  for  all  Purposes i2mo,  *3  50 

Stanley,  H.    Practical  Applied  Physics (In  Press.) 

Stansbie,  J.  H.    Iron  and  Steel.     (Westminster  Series.) 8vo,  *2  oo 

Steadman,  F.  M.     Unit  Photography i2mo,  *2  oo 

Stecher,  G.  E.     Cork.    Its  Origin  and  Industrial  Uses i2mo,  i  oo 

Steinman,  D.  B.     Suspension  Bridges  and  Cantilevers.     (Science  Series 

No.  127.) o  50 

—  Melan's   Steel  Arches  and  Suspension  Bridges 8vo,  *3  oo 

Stevens,   E.  J.     Field   Telephones  and  Telegraphs i  oo 

Stevens,  H.  P.    Paper  Mill  Chemist i6mo,  *2  50 

Stevens,  J.  S.     Theory  of  Measurements i2mo,  *i  25 

Stevenson,  J.  L.    Blast-Furnace  Calculations i2mo,  leather,  *2  oo 

Stewart,  G.     Modern  Steam  Traps i2mo,  *i  25 

Stiles,  A.     Tables  for  Field  Engineers i2mo,  i  oo 

Stodola,  A.    Steam  Turbines.    Trans,  by  L.  C.  Loewenstein 8vo,  *$  oo 

Stone,  H.    The  Timbers  of  Commerce 8vo,  3  50 

Stopes,  M.     Ancient  Plants 8vo,  *2  oo 

The  Study  of  Plant  Life 8vo,  *2  oo 

Sudborough,  J.  J.,  and  James,  T.  C.    Practical  Organic  Chemistry. .  I2mo,  *2  oo 

Suffling,  E.  R.     Treatise  on  the  Art  of  Glass  Painting 8vo,  *3  50 

Sullivan,  T.  V.,  and  Underwood,  N.    Testing  and  Valuation  of  Build- 
ing and  Engineering  Materials (In  Press.) 


28       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Sur,  F.  J.  S.     Oil  Prospecting  and  Extracting 8vo,  *i  oo 

Svenson,   C.  L.     Handbook  on  Piping 8vo,  3  oo 

Swan,  K.    Patents,  Designs  and  Trade  Marks.     (Westminster  Series.). 

8vo,  *2  oo 
Swinburne,  J.,  Wordingham,  C.  H.,  and  Martin,  T.  C.    Electric  Currents. 

(Science  Series  No.  109.) i6mo,  o  50 

Swoope,  C.  W.    Lessons  in  Practical  Electricity i2mo,  *2  oo 

Tailfer,  L.     Bleaching  Linen  and  Cotton  Yarn  and  Fabrics 8vo,  6  oo 

Tate,  J.  S.     Surcharged  and  Different  Forms  of  Retaining-walls.    (Science 

Series  No.  7.) l6mo»  °  5<> 

Taylor,  F.  N.     Small  Water  Supplies i2mo,  *2  50 

Masonry  in  Civil  Engineering 8vo,  *2  50 

Taylor,  T.  U.     Surveyor's  Handbook i2mo,  leather,  *2  oo 

Backbone  of  Perspective i2mo,  *i  oo 

Taylor,  W.   P.     Practical   Cement  Testing 8vo,  *s  oo 

Templeton,  W.    Practical  Mechanic's  Workshop  Companion. 

i2mo,  morocco,  2  oo 
Tenney,    E.    H.      Test    Methods    for    Steam    Power    Plants.      (Van 

Nostrand's  Textbooks.)    i2mo,  *2  50 

Terry,  H.  L.    India  Rubber  and  its  Manufacture.     (Westminster  Series. ) 

8vo,  *2  oo 
Thayer,  H.  R.     Structural  Design.    8vo. 

Vol.     I.    Elements  of  Structural  Design *2  oo 

Vol.   II.    Design  of  Simple  Structures *4  oo 

Vol.  III.    Design  of  Advanced  Structures (In  Preparation.) 

Foundations  and  Masonry (In   Preparation.) 

Thiess,  J.  B.,  and  Joy,  G.  A.    Toll  Telephone  Practice 8vo,  *3  50 

Thorn,  C.,  and  Jones,  W.  H.    Telegraphic  Connections.. .  .oblong,  i2mo,  150 

Thomas,  C.  W.    Paper-makers'  Handbook (In  Press.) 

Thompson,  A.  B.     Oil  Fields'  of  Russia 4to,  *7  50 

Oil  Field  Development 7  50 

Thompson,  S.  P.    Dynamo  Electric  Machines.     (Science  Series  No.  75.) 

i6mo,  o  50 

Thompson,  W.  P.    Handbook  of  Patent  Law  of  All  Countries i6mo,  i  50 

Thomson,  G.    Modern  Sanitary  Engineering i2mo,  *3  oo 

Thomson,  G.  S.     Milk  and  Cream  Testing i2mo,  *i  75 

Modern  Sanitary  Engineering,  House  Drainage,  etc 8vo,  *3  oo 

Thornley,  T.     Cotton  Combing  Machines 8vo,  *3  oo 

Cotton  Waste 8vo,  *3  oo 

• Cotton  Spinning.    8vo. 

First  Year *i  50 

Second  Year *3  oo 

Third  Year *2  50 

Thurso,  J.  W.    Modern  Turbine  Practice 8vo,  *4  oo 

Tidy,  C.  Meymott.    Treatment  of  Sewage.     (Science  Series  No.  94.)! 6mo,  o  50 
Tillmans,   J.    Water   Purification   and   Sewage   Disposal.    Trans,   by 

Hugh  S.  Taylor 8vo,  *2  oo 

Tinney,  W.  H.     Gold-mining  Machinery 8vo,  *3  oo 

Titherley,  A.  W.    Laboratory  Course  of  Organic  Chemistry 8vo,  *2  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  29 

Tizard,  H.  T.    Indicators (/M  Press.') 

Toch,  M.     Chemistry  and  Technology  of  Paints 8vo,  *4  oo 

-  Materials  for  Permanent  Painting i2mo,  *2  oo 

Tod,  J.,  and  McGibbon,  W.  C.     Marine   Engineers'   Board   of  Trade 

Examinations    8vo,  *2  oo 

Todd,  J.,  and  Whall,  W.  B.     Practical  Seamanship 8vo,  8  oo 

Tonge,  J.     Coal.     (Westminster  Series.) 8vo,  *2  oo 

Townsend,  F.     Alternating  Current  Engineering 8vo,  boards,  *o  75 

Townsend,  J.  S.     lonization  of  Gases  by  Collision 8vo,  *i  25 

Transactions  of  the  American  Institute  of  Chemical  Engineers,     8vo. 

Eight  volumes  now  ready.    Vol.  I.  to  IX.,  1908-1916 8vo,  each,  6  oo 

Traverse  Tables.     (Science  Series  No.  115.) i6mo,  o  50 

morocco,  i  oo 

Treiber,  E.    Foundry  Machinery.    Trans,  by  C.  Salter i2mo,  i  50 

Trinks,  W.,  and  Housum,  C.     Shaft  Governors.     (Science  Series  No.  122.) 

i6mo,  o  50 

Trowbridge,  W.  P.     Turbine  Wheels.     (Science  Series  No.  44.) .  .  i6mo,  o  50 

Tucker,  J.  H.     A  Manual  of  Sugar  Analysis 8vo,  3  50 

Tunner,  P.  A.     Treatise  on  Roll-turning.     Trans,  by  J.  B.  Pearse. 

8vo,  text  and  folio  atlas,  10  oo 
Turnbull,  Jr.,  J.,  and  Robinson,  S.  W.     A  Treatise  on  the  Compound 

Steam-engine.     (Science  Series  No.  8.) i6mo, 

Turner,  H.     Worsted  Spinners'  Handbook i2mo,  *2  oo 

Turrill,  S.  M.    Elementary  Course  in  Perspective i2mo,  *i  25 

Twyford,  H.  B.     Purchasing 8vo,  *$  oo 

Tyrrell,  H.  G.    Design  and  Construction  of  Mill  Buildings 8vo,  *4  oo 

Concrete  Bridges  and  Culverts i6mo,  leather,  *3  oo 

Artistic    Bridge   Design 8vo,  *s  oo 

Underbill,  C.  R.     Solenoids,  Electromagnets  and  Electromagnetic  Wind- 
ings   i2mo,  *2  oo 

Underwood,   N.,  and  Sullivan,  T.  V.     Chemistry  and   Technology   of 

Printing    Inks    8vo,  *3  oo 

Urquhart,  J.  W.    Electro-plating i2mo,  2  oo 

Electrotyping i2mo,  2  oo 

Usborne,  P.  O.  G.     Design  of  Simple  Steel  Bridges 8vo,  *4  oo 

Vacher,  F.    Food  Inspector's  Handbook  i2mo, 

Van  Nostrand's  Chemical  Annual.     Fourth  issue  1918.  .leather,  i2mo,  *3  oo 

—  Year  Book  of  Mechanical  Engineering  Data (In  Press^.} 

Van  Wagenen,  T.  F.     Manual  of  Hydraulic  Mining i6mo,  i  co 

Vega,  Baron  Von.     Logarithmic  Tables 8vo,  cloth,  2  oo 

half  morroco,  2  50 

Vincent,  C.     Ammonia  and  its  Compounds.     Trans,  by  M.  J.  Salter .  8vo,  *2  oo 

Volk,  C.     Haulage  and  Winding  Appliances 8vo,  *4  oo 

Von  Georgievics,  G.     Chemical  Technology  of  Textile  Fibres.     Trans. 

by  C.  Salter 8vo,  *4  5o 

—  Chemistry  of  Dyestuffs.     Trans,  by  C.  Salter 8vo,  *4  5° 

Vose,  G.  L.     Graphic  Method  for  Solving  Certain  Questions  in  Arithmetic 

and  Algebra      (Science  Series  No.  16.) i6mo,  o  So 


3o        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Vosmaer,  A.     Ozone 8vo,  *2  50 

Wabner,  R.    Ventilation  in  Mines.    Trans,  by  C.  Salter 8vo,  *4  50 

Wade,  E.  J.     Secondary  Batteries 8vo,  *4  o<> 

Wadmore,  T.  M.     Elementary  Chemical  Theory i2mo,  *i  50 

Wadsworth,  C.     Primary  Battery  Ignition i2mo,  *o  50 

Wagner,  E.    Preserving  Fruits,  Vegetables,  and  Meat i2mo,  *2  50 

Wagner,  J.  B.    A  Treatise  on  the  Natural  and  Artificial  Processes  of 

Wood   Seasoning >.  .8vo,  3  oo 

Waldram,  P.  J.     Principles  of  Structural  Mechanics i2mo,  *3  oo 

Walker,  F.     Aerial  Navigation 8vo,  2  oo 

Dynamo  Building.     (Science  Series  No.  98.) i6mo,  o  50 

Walker,  J.     Organic  Chemistry  for  Students  of  Medicine 8vo,  *2  50 

Walker,  S.  F.     Steam  Boilers,  Engines  and  Turbines 8vo,  3  oo 

Refrigeration,  Heating  and  Ventilation  on  Shipboard i2mo,  *2  oo 

Electricity  in  Mining 8vo,  *3  50 

Wallis-Tayler,  A.  J.     Bearings  and  Lubrication 8vo,  *i  50 

Aerial   or  Wire   Ropeways 8vo,  *3  oo 

Sugar  Machinery i2mo,  *2  oo 

Walsh,  J.  J.     Chemistry  and  Physics  of  Mining  and  Mine  Ventilation, 

i2mo,  *2  oo 

Wanklyn,  J.  A.    Water  Analysis i2mo,  2  oo 

Wansbrough,  W.  D.    The  A  B  C  of  the  Differential  Calculus i2mo,  *i  50 

Slide  Valves i2mo,  *2  oo 

Waring,  Jr.,  G.  E.    Sanitary  Conditions.    (Science  Series  No.  31.)  .i6mo,  o  50 

Sewerage  and  Land  Drainage *6  oo 

Modern  Methods  of  Sewage  Disposal i2mo,  2  oo 

—  How  to  Drain  a  House i2mo,  i  25 

Warnes,  A.  R.    Coal  Tar  Distillation 8vo,  *3  oo 

Warren,  F.  D.    Handbook  on  Reinforced  Concrete i2mo,  *2  50 

Watkins,  A.     Photography.     (Westminster  Series.). 8vo,  *2  oo 

Watson,  E.  P.    Small  Engines  and  Boilers i2mo,  i  25 

Watt,  A.     Electro-plating  and  Electro-refining  of  Metals 8vo,  *4  50 

Electro-metallurgy i2mo,  i  oo 

The  Art  of  Soap  Making 8vo,  3  oo 

Leather  Manufacture '. , .  8vo,  *4  oo 

Paper-Making 8vo,  3  oo 

Webb,  H.  L.  Guide  to  the  Testing  of  Insulated  Wires  and  Cables.  i2mo,  i  oo 

Webber,  W.  H.  Y.    Town  Gas.     (Westminster  Series.) 8vo,  *2  oo 

Wegmann,    Edward.      Conveyance    and    Distribution    of    Water    for 

Water  Supply 8vo.    (In  Press) 

Weisbach,  J.     A  Manual  of  Theoretical  Mechanics 8vo,  *6  oo 

sheep,  *y  50 

Weisbach,  J.,  and  Herrmann,  G.    Mechanics  of  Air  Machinery. ..  .8vo,  *3  75 

Wells,   M.   B.     Steel  Bridge  Designing 8vo,  *2  50 

Weston,  E.  B.    Loss  of  Head  Due  to  Friction  of  Water  in  Pipes.  .i2mo,  *i  5° 

Wheatley,  0.     Ornamental  Cement  Work 8vo,  *2  oo 

Whipple,  S.    An  Elementary  and  Practical  Treatise  on  Bridge  Building. 

8vo,  3  oo 
White,  C.  H.     Methods  »f  Metallurgical  Analysis.     (Van  Nostrand's 

Textbooks.) i2mo,  2  50 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  31 

White,  G.  F.    Qualitative  Chemical  Analysis 12 mo,  *i  25 

White,  G.  T.    Toothed  Gearing i2mo,  *i  25 

Widmer,  E.  J.     Military  Balloons 8vo,  3  oo 

Wilcox,  R.  M.      Cantilever  Bridges.     (Science  Series  No.  25.) ...  .i6mo,  o  50 

Wilda,  H.     Steam  Turbines.    Trans,  by  C.  Salter i2mo,  i  50 

—  Cranes  and  Hoists.    Trans  by  C.  Salter i2mo,  i  50 

Wilkinson,  H.  D.     Submarine  Cable  Laying  and  Repairing 8vo,  *6  oo 

Williamson,  J.     Surveying 8vo,  *s  oo 

Williamson,  R.  S.     On  the  Use  of  the  Barometer 4to,  15  oo 

—  Practical  Tables  in  Meteorology  and  Hypsometery 4to,  2  50 

Wilson,  F.  J.,  and  Heilbron,  I.  M.     Chemical  Theory  and  Calculations. 

I2IT10,  *I    OO 

Wilson,  J.  F.    Essentials  of  Electrical  Engineering 8vo,  2  50 

Wimperis,  H.  E.    Internal  Combustion  Engine 8vo,  *3  oo 

Application  of  Power  to  Road  Transport : i2mo,  *i  50 

—  Primer  of  Internal  Combustion  Engine i2mo,  *i  oo 

Winchell,  N.  H.,  and  A.  N.    Elements  of  Optical  Mineralogy 8vo,  *s  50 

Winslow,  A.    Stadia  Surveying.     (Science  Series  No.  77.) i6mo,  o  50 

Wisser,  Lieut.  J.  P.     Explosive  Materials.      (Science  Series  No.  70.) 

i6mo,  o  50 

Wisser,  Lieut.  J.  P.  Modern  Gun  Cotton.    (Science  Series  No.  89.)  .io~mo,  o  50 

Wolff,  C.  E.     Modern  Locomotive  Practice 8vo,  *4  20 

Wood,  De  V.    Luminiferous  Aether.     (Science  Series  No.  85)...i6mo,  o  50 
Wood,  J.  K.     Chemistry  of  Dyeing.     (Chemical  Monographs  No.  2.) 

i2mo,  *i  oo 

Worden,  E.  C.     The  Nitrocellulose  Industry.     Two  Volumes 8vo,  *io  oo 

Technology  of  Cellulose  Esters.     In  10  volumes.     8vo. 

Vol.  VIII.     Cellulose  Acetate *5  oo 

Wren,  H.    Organometallic  Compounds  of  Zinc  and  Magnesium.    (Chem- 
ical   Monographs    No.    i.) i2ino,  *i  oo 

Wright,  A.  C.    Analysis  of  Oils  and  Allied  Substances 8vo,  *3  50 

Simple  Method  for  Testing  Painters'  Materials 8vo,  *2  50 

Wright,  F.  W.     Design  of  a  Condensing  Plant i2mo,  *i  50 

Wright,  H.  E.     Handy  Book  for  Brewers 8vo,  *5  oo 

Wright,  J.     Testing,  Fault  Finding,  etc.,  for  Wiremen.      (Installation 

Manuals  Series.) i6mo,  *o  50 

Wright,  T.  W.     Elements  of  Mechanics 8vo,  *2  50 

Wright,  T.  W.,  and  Hayford,  J.  F.    Adjustment  of  Observations.  ..8vo,  *3  oo 
Wynne,  W.  E.,  and  Sparagen,  W.     Handbook  of  Engineering  Mathe- 
matics    8vo,  *2  oo 

Yoder,  J.  H.,  and  Wharen,  G.  B.    Locomotive  Valves  and  Valve  Gears, 

8vo,  *s  oo 

Young,  J.  E.    Electrical  Testing  for  Telegraph  Engineers 8vo,  *4  oo 

Youngson.     Slide  Valve  and  Valve  Gears 8vo,  3  oo 

Zahner,  R.    Transmission  of  Power.     (Science  Series  No.  4o.)..i6mo, 

Zeidler,  J.,  and  Lustgarten,  J.     Electric  Arc  Lamps 8vo,  *2^oo 

Zeuner,  A.    Technical  Thermodynamics.    Trans,  by  J.  F.  Klein.    Two 

Volumes 8vo,  *8  oo 

Zimmer,  G.  F.     Mechanical  Handling  and  Storing  of  Materials.  .. -4to,  *i2  50 

Zipser,  J.    Textile  Raw  Materials.    Trans,  by  C.  Salter 8vo,  *5  oo 

Zur  Nedden,  F.    Engineering  Workshop  Machines  and  Processes.   Trans. 

by  J.  A.  Davenport 8vo,  *2  oo 


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